Respuesta :

MathPhys

Step-by-step explanation:

Use the angle difference formula for cosine.

cos(α − β) = cos α cos β + sin α sin β

cos(180° − θ) = cos 180° cos θ + sin 180° sin θ

cos(180° − θ) = (-1) cos θ + (0) sin θ

cos(180° − θ) = -cos θ