Question

Please help with this question.

Answer 1

(cos Ф -cos Ф)² + (cos Ф + cos Ф)²

Firstly: (cos Ф -cos Ф)² = 0² = 0

Secondly :(cos Ф + cos Ф)² = (2cos Ф)². = 4. (cos Ф)² = 4cos² Ф

Mind you when you raise a cosine (or sin or tan...) to the n power, the n power should affect the cosine only and NOT the angle Ф