Introduction to Right Triangle Trigonometry

Right Triangle Trigonometry

An Introduction

Sides of a Right Triangle

• The HYPOTENUSE is directly across from the right angle.

• The OPPOSITE side is directly across from the referenced angle.

• The ADJACENT side is the last side. It is the side that touches the angle, but isn't the hypotenuse.

The Angle

The referenced angle could be indicated by the Greek symbol "theta", by an arc marking it, or by a measure placed in the figure. It could also be marked with an "x" or other variable if you're expected to use trig to find its measure.

Multiple Choice

Which part of the right triangle is side BC?

• hypotenuse

• opposite

• adjacent

Multiple Choice

Which part of the right triangle is side AC?

• hypotenuse

• opposite

• adjacent

Multiple Choice

Which part of the right triangle is side AB?

• hypotenuse

• opposite

• adjacent

Trigonometric Ratios

Remember, each of these ratios relies on you identifying the sides of the triangle based on your reference angle.

Multiple Choice

What is the correct trigonometric ratio for the sine of A?

Multiple Choice

What is the correct trigonometric ratio for the cosine of B?

Multiple Choice

What is the correct trigonometric ratio for the tangent of A?

Multiple Choice

What is the correct trigonometric ratio for the sine of B?

Algebra Shortcuts

These are the shortcut triangles for each of the trigonometric functions. Remember when using them, you should always put the side measure into the calculator first.

Multiple Choice

Find the length of the missing side to the nearest tenth.

• 10.1

• 10.9

• 25.0

• 29.1

Multiple Choice

Find the length of the missing side to the nearest tenth.

• 4.8

• 6.4

• 10.0

• 13.3

Multiple Choice

Find the measure of the angle to the nearest degree.

• 18^o

• 19^o

• 20^o

• 71^o

Multiple Choice

Find the measure of the angle to the nearest degree.

• 14^o

• 27^o

• 44^o

• 76^o