Download Triangles and Angles

Geometry OTQ
Name each part of the right triangle and
isosceles triangle.
hypotenuse
_________
leg
leg
leg
_________
_________
_________
leg
base
_________
_________
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Homework Questions?
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What will I be able to do?
Apply the Triangle Angle-Sum Theorem and
Exterior Angle Theorem
What standard will I learn?
12.0 Students find/use measures of sides/angles
of triangles
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4.2 Triangles and Angles
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HEY….THERE IS SOME WEIRD
ABOUT THE ANGLES OF A
TRIANGLE
2
1
3
m<1 + m<2 + m<3 = 180°
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Triangle Sum Theorem
The sum of the measures of the A
interior s of a ∆ is 180o.
B
C
m<A + m<B + m<C = 180°
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Ex 1
Solve for x.
90+ 36 + x = 180
126 + x = 180
36
x = 54
x
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Example 2:
One of the acute angles in a right
triangle measures 4x° and the other is
6x°. Find the value of x?
4x
6x
4x + 6x + 90= 180
10x + 90 = 180
10x=90
x=9
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Interior VS Exterior
An interior angle is formed by two sides of a
triangle. An exterior angle is formed by one
side of the triangle and extension of an adjacent
side.
4 is an exterior angle.
Exterior
Interior
<1, <2, and 3 are interior angle.
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Exterior Angle Theorem
The measure of an exterior  of a ∆ is equal to the
sum of the measures of the 2 non-adjacent interior
s.
A
m1 = mA + mB
B
1
C
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Example 3:
Find mB.
mA + mB = mBCD
15 + 2x + 3 = 5x – 60
2x + 18 = 5x – 60
78 = 3x
26 = x
Ext.  Thrm.
mB = 2x + 3
= 2(26) + 3
= 55°
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CLASSWORK
Pages 250 – 253 #’s 10, 12, 22, 24, 26,
28, 30, 36, 46
Homework is on the next slide
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HOMEWORK
Page 254 #’s 56, 60, 64, 66
Do your HOMEWORK or
zombies will be sent to
your HOUSE!!!
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