Write the value of cos2 76o + cos2 16o – cos 76o cos 16o.
Given to find the value for,
cos2 76o + cos2 16o – cos 76o cos 16o
In the above expression consider cos 76o cos 16o
[By using the trigonometric sum formula, we can say that,
cos(C+D) + cos ( C-D) = 2 cos C cos D]
Now multiply and divide this with 2, we get
Consider the full expression,
Multiplying and dividing the terms cos2 76° + cos2 16° with 2
[ by using the formula, cos 2θ = 2cos2θ – 1 � 2cos2θ = cos 2θ +1 ]
[ by using the formula, cos A + cos B ]
Hence, cos2 76o + cos2 16o – cos 76o cos 16o