The value of the expression $cos^2 45° + cos^2 135° + cos^2 225° + cos^2 315°$ is:
Answer & explanation
Correct answer: option 1
cos² 45° + cos² 135° + cos² 225° + cos² 315°
= cos² 45° + cos² ( 90° + 45° ) + cos² ( 180° + 45° ) + cos² ( 360° - 45° )
= cos² 45° +( - sin 45°) + (- cos45°)² + cos² 45°
= \(\frac{1}{2}\) + \(\frac{1}{2}\) + \(\frac{1}{2}\) + \(\frac{1}{2}\)
= 2