MCF3M1
Date: ___________
Lesson 1- Reviewing the Primary Trigonometric Ratios
Recall: SOH CAH TOA
A
Sin  =
O – Opposite
H – Hypotenuse
A - Adjacent
B
O
H
Cos  =
A
H
Tan =
O
A
C
Note: To solve a triangle means to find all unknown sides and angles.
You can use your calculator to find the sin, cos or tan of any angle.
Example 1:
Evaluate.
a) sin 53˚
b) cos 86˚
c) tan 71˚
You can also use your calculator to find the value of an angle, given its sin, cos or tangent value.
Example 2:
Find the measure of each angle.
a) sin A = 0.7183
b) cos C = 0.9781
c) tan X = 1.1788
We can also use trig to solve for missing side lengths and angles. Refer to the handout “What’s
My Triaingle” for assistance with this.
Example 3:
Find the lengths of the missing sides (x) in the given triangles.
a)
37o
x
What Do I Have?
What Do I Need?
10 cm
What Should I Use?
MCF3M1
b)
What Do I Have?
x
What Do I Need?
53o
17 cm
c)
What Should I Use?
What Do I Have?
7.6 cm
x
What Do I Need?
What Should I Use?
3.6 cm
Example 4:
Find the measure of the missing angles (  ).
a)
What Two Sides Do I Have?
12 cm

What Should I Use?
5 cm
b)

What Two Sides Do I Have?
9 cm
What Should I Use?
15 cm