G Tewani Solutions for Chapter: Trigonometric Ratios for Compound, Multiple, Sub-multiple Angles, and Transformation Formulas, Exercise 1: DPP

The value of $\cos 65°\cos 55°\cos 5°=$

If $\sin A+\sin 2A=x$ and $\text{cos}A+\cos 2A=y,$ then $\left(x^2+y^2\right)\left(x^2+y^2 -3\right)=$

If $\sin \theta +\sin 2\theta +\sin 3\theta =\sin \alpha$ and $\cos \theta +\cos 2\theta +\cos 3\theta =\cos \alpha ,$ then $\theta$ is equal to

The value of $\frac{\sin 22°\cos 8°+\cos 158°\cos 98°}{\sin 23°\cos 7°+\cos 157°\cos 97°}=$

The value of $\frac{\cos 5°\cos 20°+\cos 35°\cos 50°-\sin 5°\sin 20°-\sin 35°\sin 50°}{\sin 5°\cos 20°-\sin 35°\cos 50°+\cos 5°\sin 20°-\cos 35°\sin 50°}=$

The value of $\sec 11°\sec 19°-2\cot 71°$ is

 If $\alpha , \beta , \gamma$ are acute angles and $\cos \theta =\frac{ \sin \beta }{\sin \alpha }, \cos \varphi =\frac{ \sin \gamma }{\sin \alpha }$and $\cos (\theta -\varphi )=\sin \beta \sin \gamma ,$ then the value of${\tan }^2\alpha - {\tan }^2\beta - {\tan }^2\gamma$ is

In $∆ABC$ if $\tan \frac{A}{2}$, $\tan \frac{B}{2}$, $\tan \frac{C}{2}$ are in A.P., then $\cos A, \cos B, \cos C$ are in