Intro to . Part 1

What is Trigonometry?

• Trig. is the branch of mathematics that studies the ratios between the sides and angles of triangles which can then be used in many other areas of math.

• These ratios are:

– Sine, pronounced “sign”

– Cosine, pronounced “co-sign”

– Tangent

Why Trig?

• If you want to find missing sides or angles in a right triangle BUT:

– You can’t use Pythag. Theorem bc you don’t have 2 of the 3 sides.

– You can’t use 45-45-90 tricks bc you don’t have THOSE angles.

– You can’t use 30-60-90 tricks bc you don’t have THOSE angles.

• THEN YOU USE TRIG!!!

Some basic terms:

Opposite: The side directly across from the reference angle.

Hypotenuse: The side directly across from the right angle. Adjacent: The leg next

to the reference angle that is NOT the hypotenuse. (Use process of elimination to find this side last.)

Reference Angle: ONE of the 2 ACUTE angles in the right triangle. From this angle you will name the 3 sides like below.

Some basic terms:

Opposite: The side directly across from the reference angle.

Hypotenuse: The side directly across from the right angle.

Adjacent: The leg next to the reference angle that is NOT the hypotenuse. (Use process of elimination to find this side last.)

Reference Angle

So how do we find those missing sides/angles?

If you like steps

1. Pick an ACUTE reference angle.

2. Label sides Opp, Adj, & Hyp based on #1.

3. Ask these questions to decide which part of SohCahToa to use:

1. What was I given?

2. What am I finding?

4. Set up equation using SohCahToa

5. Solve using algebra.

Solve each right Triangle.

1.)

3.)