CK-12 Geometry-Concepts

8.7. Trigonometric Ratios with a Calculator http://www.ck12.org

Vocabulary

Trigonometryis the study of the relationships between the sides and angles of right triangles. The legs are called
adjacentoroppositedepending on whichacuteangle is being used. The three trigonometric (or trig) ratios aresine,
cosine, andtangent.

Guided Practice

1. What is tan 45◦?


2. Find the length of the missing sides and round your answers to the nearest tenth:

.

3. Find the length of the missing sides and round your answers to the nearest tenth:

.

Answers:

1. Using your calculator, you should find that tan 45◦=1?


2. Use tangent forxand cosine fory.

tan 28◦=

x

11

cos 28◦=

11

y

11 ·tan 28◦=x

11

cos 28◦

=y

x≈ 5. 8 y≈ 12. 5

3. Use tangent foryand cosine forx.

tan 40◦=

y

16

cos 40◦=

16

x

16 ·tan 40◦=y

16

cos 40◦

=x

y≈ 13. 4 x≈ 20. 9