Introduction

Trigonometry is based upon ratios of the sides of right triangles.

Trigonometry establishes six ratios called trigonometric functions. In this lesson, we will study the first 3...

• sine

• cosine, and

• tangent

The objective of this lesson is to demonstrate how to use sine, cosine, and tangent to calculate the missing angles of right triangles.

Summary: Deciding on the trig function to use

1. Assign a variable to the unknown angle: Using example 3 above, let our variable be x.

2. Deciding on the trig function to use: Using example 3 above, we will use sine.

3. Set up the equation:

Sin x = 39/44

4. Isolate the unknown, multiply both sides by 19

NOTE:

We write SINE(the angle) and NOT sin(a side)

So, we write sine (x) and NOT sine (39) or sine(44)

Why?: x is an angle, and 39 and 44 are sides

• Sin^-1 (39/44) = x

• 62.4 = x

• 14.15 = x