8.7. Trigonometric Ratios with a Calculator http://www.ck12.org
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. Use sineb, andcosineto finda. Use your calculator to evaluate the sine and cosine of
the angles.
sin 22◦=
b
30cos 22◦=
a
30
30 ·sin 22◦=b 30 ·cos 22◦=a
b≈ 11. 2 a≈ 27. 8Example 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◦=dc=9
cos 42◦
≈ 12. 1 d≈ 27. 0Any 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.
MEDIA
Click image to the left for more content.CK-12 Foundation: Chapter8TrigonometricRatioswithaCalculatorB
Concept Problem Revisited
Use trigonometric ratios to find the missing sides. Round to the nearest tenth.
Find the length ofaandbusing sine or cosine ratios: