MCQ
$\sin\alpha-\sin\beta=a,\cos\alpha+\cos\beta=b$ તો $a^2+b^2....$થી વધુ ન હોય.
- A3
- ✓4
- C1
- D32
$a^2+b^2=(\sin\alpha-\sin\beta)^2+(\cos\alpha+\cos\beta)^2$
$=\sin^2\alpha-2\sin\alpha\sin\beta+\sin^2\beta+\cos^2\alpha+2\cos\alpha\cos\beta+\cos^2\beta$
$=2+2\cos(\alpha+\beta)$
$=2\left(2\cos^2\left(\frac{\alpha+\beta}{2}\right)\right)\leq4$
નોંધ $:\alpha=\beta=0$ માટે મૂલ્ય $4$ બને.
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