the value of cos20 degree cos70 degree_ sin20 degree sin70 degree
Answers
cos(70^@)*cos(20^@)-sin(70^@)*sin(20^@) = 0
Explanation:
The Cosine Sum of Angles Formula tells us
cos(a+b) = cos(a)*cos(b)-sin(a)*sin(b)
Substituting 70^@ for a
and 20^@ for b
we have
cos(90^@)=cos(70^@)*cos(20^@)-sin(70^@)*sin(20^@)
and we know
cos(90^@) = 0
Nghi N.
Oct 19, 2015
Answer:
Find (cos 70.cos 20 - sin 70.sin 20)
Ans: 0
Explanation:
Use the trig identity: cos (a + b) = cos a.cos b - sin a.sin b -->
(cos 70.cos 20 - sin 70.sin 20) = cos (70 + 20) = cos (90^@) = 0
Related topic
Trigonometric Functions of Any Angle
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