If $5\cos 2\theta + 2{\cos ^2}\frac{\theta }{2} + 1 = 0, - \pi < \theta < \pi $, then $\theta = $
$\frac{\pi }{3}$
$\frac{\pi }{3},{\cos ^{ - 1}}\frac{3}{5}$
${\cos ^{ - 1}}\frac{3}{5}$
$\frac{\pi }{3},\pi - {\cos ^{ - 1}}\frac{3}{5}$
Find the principal and general solutions of the equation $\sec x=2$
Let $f(x) = \cos \sqrt {x,} $ then which of the following is true
The sum of all values of $x$ in $[0,2 \pi]$, for which $\sin x+\sin 2 x+\sin 3 x+\sin 4 x=0$, is equal to:
The equation $5x^2+12x + 13 = 0$ and $ax^2+bx + c = 0$ have a common root, where $a,b,c$ are the sides of $\Delta ABC$,then find $\angle C$ ? .....$^o$
If $\alpha ,$ $\beta$ are different values of $x$ satisfying $a\cos x + b\sin x = c,$ then $\tan {\rm{ }}\left( {\frac{{\alpha + \beta }}{2}} \right) = $