Question

If $$\tan \theta + \tan \left( {\theta + \frac{\pi }{3}} \right) + \tan \left( {\theta - \frac{\pi }{3}} \right) = k\tan 3\theta $$          then $$k$$ is equal to

A. $$1$$
B. $$3$$  
C. $${\frac{1}{3}}$$
D. None of these
Answer :   $$3$$
Solution :
$$\eqalign{ & {\text{L}}{\text{.H}}{\text{.S}} = \tan \theta + \frac{{\tan \theta + \sqrt 3 }}{{1 - \sqrt 3 \tan \theta }} + \frac{{\tan \theta - \sqrt 3 }}{{1 + \sqrt 3 \tan \theta }} \cr & {\text{L}}{\text{.H}}{\text{.S}} = \frac{{\left\{ {\tan \theta - 3{{\tan }^3}\theta + \left( {\tan \theta + \sqrt 3 } \right)\left( {1 + \sqrt 3 \tan \theta } \right) + \left( {\tan \theta - \sqrt 3 } \right)\left( {1 - \sqrt 3 \tan \theta } \right)} \right\}}}{{1 - 3{{\tan }^2}\theta }} \cr & {\text{L}}{\text{.H}}{\text{.S}} = \frac{{3\left( {3\tan \theta - {{\tan }^3}\theta } \right)}}{{1 - 3{{\tan }^2}\theta }} = 3\tan 3\theta ; \cr & \therefore \,\,\,\,k = 3. \cr} $$

Releted MCQ Question on
Trigonometry >> Trigonometric Ratio and Identities

Releted Question 1

If $$\tan \theta = - \frac{4}{3},$$   then $$\sin \theta $$  is

A. $$ - \frac{4}{5}{\text{ but not }}\frac{4}{5}$$
B. $$ - \frac{4}{5}{\text{ or }}\frac{4}{5}$$
C. $$ \frac{4}{5}{\text{ but not }} - \frac{4}{5}$$
D. None of these
Releted Question 2

If $$\alpha + \beta + \gamma = 2\pi ,$$    then

A. $$\tan \frac{\alpha }{2} + \tan \frac{ \beta }{2} + \tan \frac{\gamma }{2} = \tan \frac{\alpha }{2}\tan \frac{\beta }{2}\tan \frac{\gamma }{2}$$
B. $$\tan \frac{\alpha }{2}\tan \frac{\beta }{2} + \tan \frac{\beta }{2}\tan \frac{\gamma }{2} + \tan \frac{\gamma }{2}\tan \frac{\alpha }{2} = 1$$
C. $$\tan \frac{\alpha }{2} + \tan \frac{ \beta }{2} + \tan \frac{\gamma }{2} = - \tan \frac{\alpha }{2}\tan \frac{\beta }{2}\tan \frac{\gamma }{2}$$
D. None of these
Releted Question 3

Given $$A = {\sin ^2}\theta + {\cos ^4}\theta $$    then for all real values of $$\theta $$

A. $$1 \leqslant A \leqslant 2$$
B. $$\frac{3}{4} \leqslant A \leqslant 1$$
C. $$\frac{13}{16} \leqslant A \leqslant 1$$
D. $$\frac{3}{4} \leqslant A \leqslant \frac{{13}}{{16}}$$
Releted Question 4

The value of the expression $$\sqrt 3 \,{\text{cosec}}\,{\text{2}}{{\text{0}}^ \circ } - \sec {20^ \circ }$$     is equal to

A. 2
B. $$\frac{{2\sin {{20}^ \circ }}}{{\sin {{40}^ \circ }}}$$
C. 4
D. $$\frac{{4\sin {{20}^ \circ }}}{{\sin {{40}^ \circ }}}$$

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