Lesson 7.7Goal: The students will use inverse sine, cosine

and tangent ratios.m

These find the angle measure, not the ratio.

Inverse Trigonometry Ratios

C b A

B

a c

tan A = .5698 Find A.

cos A = .3921 Find A.

sin A = .9067 Find A.

How to use the calculator

Press the 2nd button to access inverse sine, cosine and tangent.

Find angle A.

Find the angle measure.

1. Decide which trigonometric ration to use.2. Set up equation.3. Go ahead and solve.

Let A and B be acute angles in a right triangle. Use a calculator to approximate the measures of A and B to the nearest tenth of a degree.

a. sin A = 0.87

b. cos B = 0.15

This means find any missing angle measure and side length.

Solve a Right Triangle

AC

B

42˚

12

Solve the Right Triangle

Suppose your school is building a raked stage. The stage will be 30 feet long from front to back, with a total rise of 2 feet. A rake (angle of elevation) of 5o or less is generally preferred for the safety and comfort of the actors. Is the raked stage you are building within the range suggested?

P. 485 # 1, 3,6,7, 10-12, 19, 20, 21-23, 25

Assignment