Wiskunde Multiple Choice Vraag uit Gricha's Wiskundige Vragenbank

cos²150° − cos²60° =	A. − 1
B.
C. 0
D.
E. 1

(cos 150°)² − (cos 60°)² =	A. − 1
	B.
	C. 0
	D.
	E. 1

$\cos^2 150^\circ - \cos^2 60^\circ \\ = (\cos 150^\circ)^2 - (\cos 60^\circ)^2 \\ = (-\cos 30^\circ)^2 - (\cos 60^\circ)^2\\ = \left (-\frac{\sqrt 3}{2} \right )^2 - \left (\frac 12 \right )^2 \\ = \frac 34 - \frac 14 = \frac 24 = \frac 12$