[JEE Main 2009] statements a cos alpha cos beta cos gamma 0 b sin alpha sin beta
Statements — A: $\cos\alpha+\cos\beta+\cos\gamma=0$; B: $\sin\alpha+\sin\beta+\sin\gamma=0$. If $\cos(\beta-\gamma)+\cos(\gamma-\alpha)+\cos(\alpha-\beta)=-\frac32$, then
(a) A false, B true
(b) both true
(c) both false
(d) A true, B false
1 Answer
VAVidaara Admin
✓ Vidaara Team
✓ Accepted
· 2d ago
▲ 0
Correct answer: (b) both true
$(\sum\cos)^2+(\sum\sin)^2=3+2\sum\cos(\alpha-\beta)=3+2(-\frac32)=0$, forcing both sums to be $0$ — both A and B true.
JEE Main 2009 · Trigonometry — verified solution by the Vidaara Team.
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