Trigonometrical Equations
medium

જો $\cos A\sin \left( {A - \frac{\pi }{6}} \right)$ એ મહતમ હોય તો $A$ ની કિમત મેળવો.

A

$\frac{\pi }{3}$

B

$\frac{\pi }{4}$

C

$\frac{\pi }{2}$

D

એકપણ નહિ.

Solution

(a) $\cos A\sin \left( {A – \frac{\pi }{6}} \right) = \frac{1}{2}\,\left[ {\sin \left( {2A – \frac{\pi }{6}} \right) – \sin \frac{\pi }{6}} \right]$

But $\sin \left( {2A – \frac{\pi }{6}} \right) – \frac{1}{2}$

attain maximum value at $2A – \frac{\pi }{6} = \frac{\pi }{2} \Rightarrow A = \frac{\pi }{3}$.

Standard 11
Mathematics

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