How do you find the exact value of cos 70 cos 20 - sin 70 sin 20?
2 Answers
Oct 19, 2015
Explanation:
The Cosine Sum of Angles Formula tells us
Substituting
and
we have
and we know
Oct 19, 2015
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) =