Question

If $\Rightarrow$is maximum, then the value of A is equal to.

• A. $\theta = \frac{5\pi}{6}$
• B. $\cot\theta = \sin 2\theta,\text{ }(\theta \neq n\pi) \Rightarrow 2\sin^{2}\theta\cos\theta = \cos\theta$
• C. $\Rightarrow$
• D. None of these

Answer 1

Answer: (A)

$\theta = \frac{5\pi}{6}$

Answer 2

$B = 60^{o},$

But $\cos B = \frac{a^{2} + c^{2} - b^{2}}{2ac}$ attain maximum value at

$\left\{ \begin{aligned} & \text{since }A + B + C = 180^{o}\text{and} \\ & \text{ }A + C = 2B \Rightarrow B = 60^{o} \end{aligned} \right\}$.