CK-12 Geometry-Concepts

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

Depending on your calculator, you enter the degree and then press the trig button or the other way around. Also,
make sure the mode of your calculator is inDEGREES.

a) sin 78◦= 0. 97815

b) cos 60◦= 0. 5

c) tan 15◦= 0. 26795

Example B

Find the value of each variable. Round your answer to the nearest tenth.

We are given the hypotenuse. Usesineto findb, andcosineto finda. Use your calculator to evaluate the sine and
cosine of the angles.

sin 22◦=

b

30

cos 22◦=

a

30

30 ·sin 22◦=b 30 ·cos 22◦=a

b≈ 11. 2 a≈ 27. 8

Example C

Find the value of each variable. Round your answer to the nearest tenth.

We are given the adjacent leg to 42◦. To findc, usecosineand usetangentto findd.

cos 42◦=

ad jacent

hy potenuse

=

9

c

tan 42◦=

o p posite

ad jacent

=

d

9

c·cos 42◦= 9 9 ·tan 42◦=d

c=

9

cos 42◦

≈ 12. 1 d≈ 27. 0

Any time you use trigonometric ratios, use only the information that you are given. This will result in the most
accurate answers.

Watch this video for help with the Examples above.