Wiskunde Multiple Choice Vraag uit Gricha's Wiskundige Vragenbank

cos²150° − cos²60° =	A. $-1$
	B. $-\frac12$
	C. $0$
	D. $\frac12$
	E. $1$

[ 4-1642 - op net sinds 27.2.98-(E)-25.8.2025 ]

Translation in E N G L I S H

(cos 150°)² − (cos 60°)² =	A. $-1$
	B. $-\frac12$
	C. $0$
	D. $\frac12$
	E. $1$

Oplossing - Solution

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

cos²150° − cos²60° =	A. \(-1\)
	B. \(-\frac12\)
	C. \(0\)
	D. \(\frac12\)
	E. \(1\)

(cos 150°)² − (cos 60°)² =	A. \(-1\)
	B. \(-\frac12\)
	C. \(0\)
	D. \(\frac12\)
	E. \(1\)