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Gettin’ Triggy wit it http://www.youtube.com/watch?v=t2uPYYL H4Zo An angle is formed by joining the endpoints of two half-lines called rays. The side you measure to is called the terminal side. Angles measured counterclockwise are given a positive sign and angles measured clockwise are given a negative sign. Negative Angle This is a clockwise rotation. Positive Angle This is a counterclockwise rotation. Initial Side The side you measure from is called the initial side. It’s Greek To Me! It is customary to use small letters in the Greek alphabet to symbolize angle measurement. alpha theta beta gamma We can use a coordinate system with angles by putting the initial side along the positive x-axis with the vertex at the origin. Quadrant Quadrant I II angle angle positive negative Initial Side Quadrant If the terminal side is along IV an axis it is called a angle quadrantal angle. We say the angle lies in whatever quadrant the terminal side lies in. We will be using two different units of measure when talking about angles: Degrees and Radians = 360° If we start with the initial side and go all of the way around in a counterclockwise direction we have 360 degrees = 90° If we went 1/4 of the way in a clockwise direction the angle would measure -90° = - 90° You are probably already familiar with a right angle that measures 1/4 of the way around or 90° Let’s talk about degrees first. You are probably already somewhat familiar with degrees. What is the measure of this angle? You could measure in the positive = - 360° + 45° direction and go around another rotation which would be another 360° = - 315° = 45° You could measure in the positive direction = 360° + 45° = 405° You could measure in the negative direction There are many ways to express the given angle. Whichever way you express it, it is still a Quadrant I angle since the terminal side is in Quadrant I. If the angle is not exactly to the next degree it can be expressed as a decimal (most common in math) or in degrees, minutes and seconds (common in surveying and some navigation). 1 degree = 60 minutes 1 minute = 60 seconds = 25°48‘29" degrees seconds minutes To convert to decimal form use conversion fractions. These are fractions where the numerator = denominator but two different units. Put unit on top you want to convert to and put unit on bottom you want to get rid of. Let's convert the seconds to minutes 30" 1' 60" = 0.5' 1 degree = 60 minutes 1 minute = 60 seconds = 25°48'30" = 25°48.5' = 25.808° Now let's use another conversion fraction to get rid of minutes. 48.5' 1 60' = .808° Another way to measure angles is using what is called radians. Given a circle of radius r with the vertex of an angle as the center of the circle, if the arc length formed by intercepting the circle with the sides of the angle is the same length as the radius r, the angle measures one radian. arc length is also r r r r initial side radius of circle is r This angle measures 1 radian Arc length s of a circle is found with the following formula: IMPORTANT: ANGLE MEASURE MUST BE IN RADIANS TO USE FORMULA! s = r arc length radius measure of angle Find the arc length if we have a circle with a radius of 3 meters and central angle of 0.52 radian. arc length to find is in black = 0.52 3 s = r30.52 = 1.56 m What if we have the measure of the angle in degrees? We can't use the formula until we convert to radians, but how? We need a conversion from degrees to radians. We could use a conversion fraction if we knew how many degrees equaled how many radians. Let's start with the arc length formula cancel the r's s = r 2r = r 2 = 2 radians = 360° If we look at one revolution around the circle, the arc length would be the circumference. Recall that circumference of a circle is 2r This tells us that the radian measure all the way around is 2. All the way around in degrees is 360°. 2 radians = 360° radians = 180° Convert 30° to radians using a conversion fraction. 30° 2 radians 360 = 6 The fraction can be reduced by 2. This would be a simpler conversion fraction. 180° radians 0.52 Can leave with or use button on your calculator for decimal. Convert /3 radians to degrees using a conversion fraction. 180 radians 3 radians = 60° Area of a Sector of a Circle r The formula for the area of a sector of a circle (shown in red here) is derived in your textbook. It is: Again must be in RADIANS so if it is in degrees you must convert to radians to use the formula. 1 2 A r 2 Find the area of the sector if the radius is 3 feet and = 50° 50 radians 180 = 0.873 radians 1 2 A 3 0.873 2 3.93 sq ft A Sense of Angle Sizes 45 4 30 6 90 2 See if you can guess the size of these angles first in degrees and then in radians. 2 120 3 5 150 6 60 3 180 3 135 4 You will be working so much with these angles, you should know them in both degrees and radians. Angles, Arc length, Conversions Angle measured in standard position. Initial side is the positive x – axis which is fixed. Terminal side is the ray in quadrant II, which is free to rotate about the origin. Counterclockwise rotation is positive, clockwise rotation is negative. Coterminal Angles: Angles that have the same terminal side. 60°, 420°, and –300° are all coterminal. Degrees to radians: Multiply angle by . 60 radians 180 3 180 Radians to degrees: Multiply angle by 180 . 4 45 180 Note: 1 revolution = 360° = 2π radians. Arc length = central angle x radius, or s r. Note: The central angle must be in radian measure. 6.2 TRIGONOMETRY Remember SOHCAHTOA • Sine is Opposite divided by Hypotenuse • Cosine is Adjacent divided by Hypotenuse • Tangent is Opposite divided by Adjacent • SOHCAHTOA!!!!!! • http://www.youtube.com/watch?v=4iCgjKvc7A&feature=related Right Triangle Trig Definitions B c a C • • • • • • b A sin(A) = sine of A = opposite / hypotenuse = a/c cos(A) = cosine of A = adjacent / hypotenuse = b/c tan(A) = tangent of A = opposite / adjacent = a/b csc(A) = cosecant of A = hypotenuse / opposite = c/a sec(A) = secant of A = hypotenuse / adjacent = c/b cot(A) = cotangent of A = adjacent / opposite = b/a Special Right Triangles 30° 45° 2 2 3 1 3 cos(30 ) 2 1 sin( 30 ) 2 3 tan( 30 ) 3 1 60° 1 2 3 sin( 60 ) 2 tan( 60 ) 3 cos(60 ) 1 2 2 2 sin( 45 ) 2 tan( 45 ) 1 cos( 45 ) 45° 6.2 Assignment (day 1) pp. 417-419 (1-23 odd, 27, 29) 21, 23 Basic Trigonometric Identities Quotient identities: tan( A) Even/Odd identities: sin( A) cos( A) cos( A) sin( A) cot( A) cos( A) cos( A) sec( A) sec( A) sin( A) sin( A) csc( A) csc( A) tan( A) tan( A) cot( A) cot( A) Even functions Odd functions Odd functions Reciprocal Identities: 1 csc( A) sin( A) 1 sin( A) csc( A) 1 sec( A) cos( A) 1 cos( A) sec( A) 1 cot( A) tan( A) 1 tan( A) cot( A) Pythagorean Identities: sin 2 ( A) cos 2 ( A) 1 tan 2 ( A) 1 sec 2 ( A) 1 cot 2 ( A) csc 2 ( A) All Students Take Calculus. Quad I Quad II Quad III cos(A)<0 sin(A)>0 tan(A)<0 sec(A)<0 csc(A)>0 cot(A)<0 cos(A)>0 sin(A)>0 tan(A)>0 sec(A)>0 csc(A)>0 cot(A)>0 cos(A)<0 sin(A)<0 tan(A)>0 sec(A)<0 csc(A)<0 cot(A)>0 cos(A)>0 sin(A)<0 tan(A)<0 sec(A)>0 csc(A)<0 cot(A)<0 Quad IV • http://www.youtube.com/watch?v=Ah9NxA GzlDc&feature=related 6.3 Trigonometric Functions of Real Numbers Exact Values Using Points on the Circle • Example. Let t be a real number and P = the point on the unit circle that corresponds to t. Problem: Find the values of sin t, cos t, tan t, csc t, sec t and cot t Answer: Exact Values for Quadrantal Angles • Example. Find the values of the trigonometric functions of µ Problem: µ = 0 = 0± Answer: Exact Values for Quadrantal Angles • Example. Find the values of the trigonometric functions of µ Problem: µ = Answer: = 90± Exact Values for Quadrantal Angles • Example. Find the values of the trigonometric functions of µ Problem: µ = ¼ = 180± Answer: Circles of Radius r • Example. Problem: Find the exact values of each of the trigonometric functions of an angle θ if ({12, 5}) is a point on its terminal side. Answer: Even-Odd Properties • Theorem. [Even-Odd Properties] sin(θ) = sin(θ) cos(θ) = cos(θ) tan(θ) = tan(θ) csc(θ) = csc(θ) sec(θ) = sec(θ) cot(θ) = cot(θ) • Cosine and secant are even functions • The other functions are odd functions The Sine Function The sine of a real number t is the y–coordinate (height) of the point P in the following diagram, where |t| is the length of the arc. 1 y sin t –1 P |t| 1 unit 1 –1 x sin t sint An odd function. Properties of Sine and Cosine Functions The graphs of y = sin x and y = cos x have similar properties: 1. The domain is the set of real numbers. 2. The range is the set of y values such that 1 y 1. 3. The maximum value is 1 and the minimum value is –1. 4. The graph is a smooth curve. 5. Each function cycles through all the values of the range over an x-interval of 2 . 6. The cycle repeats itself indefinitely in both directions of the x-axis. The Sine Function 1.5 Highlight those sections of the circle where sin(t) >0 1 sin(0) 0 0.5 > 0 sin(t) 0 -1.5 -1 -0.5 0.5 -0.5 -1 -1.5 1 1.5 sin 1 2 sin 0 3 sin 2 1 The Sine Function 2 2 3 2 Graph of the Sine Function To sketch the graph of y = sin x first locate the key points. These are the maximum points, the minimum points, and the intercepts. 3 x 0 2 2 sin x 0 2 1 0 -1 0 Then, connect the points on the graph with a smooth curve that extends in both directions beyond the five points. A single cycle is called a period. y = sin x y 3 2 1 2 2 1 3 2 2 5 2 x The Cosine Function The cosine of a real number t is the x– coordinate (length) of the point P in the following diagram, where |t| is the length of the arc. y 1 –1 1 unit P |t| cos t 1 –1 x cos t cost An even function. The Cosine Function 1.5 Highlight those sections where cos(t) > 0 1 cos(0) 1 0.5 cos(t)0.5 >0 0 -1.5 -1 -0.5 -0.5 -1 -1.5 1 1.5 cos 0 2 cos 1 3 cos 2 0 The Cosine Function 2 2 3 2 Graph of the Cosine Function To sketch the graph of y = cos x first locate the key points. These are the maximum points, the minimum points, and the intercepts. 3 x 0 2 2 cos x 1 2 0 -1 0 1 Then, connect the points on the graph with a smooth curve that extends in both directions beyond the five points. A single cycle is called a period. y = cos x y 3 2 1 2 2 1 3 2 2 5 2 x Graphing the Tangent Function • Periodicity: Only need to graph on interval [0, ¼] • Plot points and graph Graphing the Cotangent Function • Periodicity: Only need to graph on interval [0, ¼] Graphing the Cosecant and Secant Functions • Use reciprocal identities • Graph of y = csc x Graphing the Cosecant and Secant Functions • Use reciprocal identities • Graph of y = sec x 6.4 Values of the Trigonometric Functions 6.4 Reference Angles • A reference angle for an angle , written , is the positive acute angle made by the terminal side of angle and the x-axis. Example Find the reference angle for each angle. (a) 218º (b) 5 6 Solution 5 (a) = 218º – 180º = 38º (b) 6 6 6.4 Special Angles as Reference Angles Example Find the values of the trigonometric functions for 210º. Solution The reference angle for 210º is 210º – 180º = 30º. Choose point P on the terminal side so that the distance from the origin to P is 2. A 30º - 60º right triangle is formed. 1 3 3 sin 210 cos 210 tan 210 2 2 3 2 3 csc 210 2 sec 210 cot 210 3 3 6.4 Finding Trigonometric Function Values Using Reference Angles Example Find the exact value of each expression. (a) cos(–240º) (b) tan 675º Solution (a) –240º is coterminal with 120º. The reference angle is 180º – 120º = 60º. Since –240º lies in quadrant II, the cos(–240º) is negative. 1 cos( 240 ) cos 60 2 Similarly, tan 675º = tan 315º = –tan 45º = –1. • Quad II Reference AnglesQuad I θ’ = 180° – θ θ’ = θ θ’ = π – θ θ’ = θ – 180° θ’ = θ – π Quad III θ’ = 360° – θ θ’ = 2π – θ Quad IV 6.4 Finding Trigonometric Function Values with a Calculator Example Approximate the value of each expression. (a) cos 49º 12 (b) csc 197.977º Solution Set the calculator in degree mode. 6.4 Finding Angle Measure Example Using Inverse Trigonometric Functions to Find Angles (a) Use a calculator to find an angle in degrees that satisfies sin .9677091705. (b) Use a calculator to find an angle in radians that satisfies tan .25. Solution (a) With the calculator in degree mode, we find that an angle having a sine value of .9677091705 is 75.4º. Write this as sin-1 .9677091705 75.4º. (b) With the calculator in radian mode, we find tan-1 .25 .2449786631. 6.4 Finding Angle Measure Example Find all values of , if is in the interval [0º, 360º) and cos 22 . Solution Since cosine is negative, must lie in either quadrant II or III. Since cos 22 , cos 1 22 45. So the reference angle = 45º. The quadrant II angle = 180º – 45º = 135º, and the quadrant III angle = 180º + 45º = 225º. 6.4 Review Answers 6.4 Review 6.5 Graphs of Trigonometric Functions 6.5 Trigonometric Graphs Objective: We will re-define the basic trig. functions and their graphs and go more in depth with vertical stretches, horizontal stretches, periods, amplitudes, and shifts up and down. Sine graphs y = sin(x) y = 3sin(x) y = sin(x) + 3 y = sin(3x) y = sin(x – 3) y = sin(x/3) y = 3sin(3x-9)+3 y = sin(x) Graphs of cosine y = cos(x) y = cos(x) + 3 y = 3cos(x) y = cos(3x) y = cos(x – 3) y = cos(x/3) y = 3cos(3x – 9) + 3 y = cos(x) 6.5 (Sine & Cosine) Review: y = sin x y = cos x a varies height/ vertical stretch of graph amplitude = |a| a varies height/ 1 vertical stretch of graph amplitude = |a| Π Π 2Π -1 y = asin(bx+c) +d *y = 3 sin x *y = ½ sin x y = acos(bx+c) +d *y = 2 cos x *y = -2cos x 2Π The amplitude of y = a sin x (or y = a cos x) is half the distance between the maximum and minimum values of the function. amplitude = |a| If |a| > 1, the amplitude stretches the graph vertically. If 0 < |a| > 1, the amplitude shrinks the graph vertically. If a < 0, the graph is reflected in the x-axis. y 4 y = 2sin x 2 y= 1 2 3 2 2 x sin x y = – 4 sin x reflection of y = 4 sin x 4 y = sin x y = 4 sin x Example: Sketch the graph of y = 3 cos x on the interval [–, 4]. Partition the interval [0, 2] into four equal parts. Find the five key points; graph one cycle; then repeat the cycle over the interval. x y = 3 cos x y (0, 3) 2 1 0 3 0 -3 x-int min 2 max 3 2 0 2 3 x-int max (2 , 3) 1 ( , 0) 2 2 3 ( , –3) 2 ( 3 , 0) 2 3 4 x Use basic trigonometric identities to graph y = f (–x) Example 1: Sketch the graph of y = sin (–x). The graph of y = sin (–x) is the graph of y = sin x reflected in the x-axis. y = sin (–x) y Use the identity sin (–x) = – sin x y = sin x x 2 Example 2: Sketch the graph of y = cos (–x). The graph of y = cos (–x) is identical to the graph of y = cos x. y Use the identity x cos (–x) = cos x 2 y = cos (–x) The period of a function is the x interval needed for the function to complete one cycle. For b 0, the period of y = a sin bx is 2 . b For b 0, the period of y = a cos bx is also 2 . b If 0 < b < 1, the graph of the function is stretched horizontally. y y sin 2 x period: 2 period: y sin x x 2 If b > 1, the graph of the function is shrunk horizontally. y y cos x 1 y cos x period: 2 2 2 3 4 x period: 4 y=asin(bx+c) +d y=acos(bx+c) +d b varies width/horizontal stretch Period = 2 Π b y = 3 sin 2x amp: |a| = per: 2 Π = b ** this means there is 1 sine wave on the interval [0, Π] ** Sketch the graph. 1 2 Y = 2sin x amp: |a| = per: 2 Π = b Graph: Example: Sketch the graph of y = 2 sin (–3x). Rewrite the function in the form y = a sin bx with b > 0 y = 2 sin (–3x) = –2 sin 3x Use the identity sin (– x) = – sin x: 2 2 period: amplitude: |a| = |–2| = 2 = 3 b Calculate the five key points. x 0 y = –2 sin 3x 0 y 2 6 3 2 2 3 –2 0 2 0 ( , 2) 6 3 6 (0, 0) 2 ( ,-2) 6 2 2 3 2 ( , 0) 2 3 ( , 0) 3 5 6 x d • y= 2sinx + 3 shifts up & down y = cosx - 2 y = asin(bx+c); phase shift = -c/b; 0≤bx+c≤2Π • y = 3 sin(2x+Π) 2 amp: |a| = per: 2 Π = b p.s. = 0 ≤ 2x+Π ≤ 2Π 2 Express in the form: y = asin(bx+c) for a,b,c,> 0 5 a= b= p.s. = -4 -2 -5 2 4 Example Determine the amplitude, period, and phase shift of y = 2sin(3x-) Solution: Amplitude = |A| = 2 period = 2/B = 2/3 phase shift = -C/B = /3 Example cont. • y = 2sin(3x- ) 3 2 1 -6 -5 -4 -3 -2 -1 -1 -2 -3 1 2 3 4 5 6 a sin( bx c) d Amplitude Period: 2π/b Phase Shift: -c/b Vertical Shift 6.6 More Trig. Graphs Objective: Students will look at more trig. graphs, including the tangent and reciprocal functions, and the variations on these reciprocal functions and their graphs. 6.6 Variations on reciprocal functions: Amplitude has no meaning (tan/cot) “a” still varies vertical stretch 2 “b” still affects period tanθ, cot θ = | b | csc θ, sec θ = | b | c “c” still affects phase shift b “d” still varies vertical shifts 6.6 y = tan x -2Π y = a tan(bx+c) +d amplitude: period: phase shift: -Π Π 2Π Successive vertical asymptotes: 2 <bx+c< 2 6.6 y= 1 2 tan (x + period: p.s. 4 ) 6.6 y = cot x y = csc x y = sec x y = csc (2x + Π) = 1 sin( 2 x ) Recall: csc θ = amp: per: p.s. 1 sin 6.7 Applied Problems Objective: Students will use trig. functions in applying real-world application problems. 6.7 Ex: (#25 from assignment) x ft. 500 ft. 60° 4 ft. SOH-CAH-TOA x sin 60 = 500 x = 433 ft + 4 = 437 Ch. 6 Test Review