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Mathematics 10
Kim
CH.3 Right Triangle Trigonometry
Trigonometry (from Greek, “triangle” and “measure”) is a branch of math that
studies relationships involve lengths and angles of triangle.
Today’s Goal: Learn how to correctly name triangles (their sides and angles) and
to use Pythagoras.
Let’s start with some definitions:
Right triangle –
Equilateral triangle-
Isosceles triangle –
Scalene triangle –
Let’s label angles and sides of triangles:
Ex.1
Draw a triangle,∆ABC, and label all angles and sides.
A
B
C
Mathematics 10
Kim
Label sides:
-One lower case: We label the side across from an angle using the same
letter, only in lower case.
-Two endpoints: Use capital letters
Label angles:
-One upper case
-Using three point system- an angle is name using the two origins of the
angle, and the vertex, with the vertex ALWAYS in the middle!
Your Turn:
Name each side with
a) one lower case.
X
Y
Z
b) two end points.
b) Name each indicated angle using the three point system.
A
B
Q
C
R
S
Mathematics 10
Kim
In this chapter, we will also want to label the sides of a RIGHT triangle based their
on their position to a target angle which we use as a reference point.
Let’s try an example.
EX.3
In reference to angle A, label:
a) Hyp, for the hypotenuse
b) Opp, for the side opposite to ∠A
c) Adj, for the side adjacent to ∠A
B
C
A
Your Turn: Repeat Ex.3 in reference to angle B.
B
C
A
Since we will be dealing with right triangles in this chapter, remembering how
to apply Pythagorean Theorem correctly is also important.
Mathematics 10
Kim
Let’s try some questions involving Pythagorean Theorem.
Ex.4
Name and find the missing sides(s) to nearest tenth.
a) A
a=10cm
c= 6cm
B
C
K
Your Turn: b)
i= 15cm
j= 11cm
J
I
HW: Chapter 3 Prerequisite Skills -#1, 4, 5, 7, 8
Cross-Multiplication Worksheet –Review the note/do #1-20- even #s only.