Question

O 131 If cos 23°=P, express without the use of a calculator the following in terms of p.

Cos203°​

Answer 1

cos203° = - p

Explanation:

Using the addition formula for cosine

cos(a + b) = cosacosb - sinasinb

cos203°

= cos(180 + 23)

= cos180°cos23° - sin180°sin23°

= cos180°. p - 0

= - 1 . p

= - p