Question

The set of values of $$x$$ for which $$\sin x \cdot {\cos ^3}x > \cos x \cdot {\sin ^3}x,0 \leqslant x \leqslant 2\pi ,$$        is

A. $$\left( {0,\pi } \right)$$
B. $$\left( {0,\frac{\pi }{4}} \right)$$  
C. $$\left( {\frac{\pi }{4},\pi } \right)$$
D. None of these
Answer :   $$\left( {0,\frac{\pi }{4}} \right)$$
Solution :
$$\eqalign{ & \sin x \cdot \cos x\left( {{{\cos }^2}x - {{\sin }^2}x} \right) > 0\,\,\,{\text{or, }}\frac{1}{2}\sin 2x \cdot \cos 2x > 0\,\,{\text{or, }}\sin 4x > 0 \cr & \therefore \,\,0 < 4x < \pi . \cr} $$

Releted MCQ Question on
Trigonometry >> Trignometric Equations

Releted Question 1

The equation $$2\,{\cos ^2}\frac{x}{2}{\sin ^2}x = {x^2} + {x^{ - 2}};0 < x \leqslant \frac{\pi }{2}$$        has

A. no real solution
B. one real solution
C. more than one solution
D. none of these
Releted Question 2

The general solution of the trigonometric equation $$\sin x + \cos x = 1$$    is given by:

A. $$x = 2n\pi ;\,\,n = 0,\,\, \pm 1,\,\, \pm 2\,.....$$
B. $$x = 2n\pi + \frac{\pi }{2};\,\,n = 0,\,\, \pm 1,\,\, \pm 2\,.....$$
C. $$x = n\pi + {\left( { - 1} \right)^n}\,\,\frac{\pi }{4} - \frac{\pi }{4}$$
D. none of these
Releted Question 3

The general solution of $$\sin \,x - 3\,\sin \,2x\, + \sin \,3x\, = \cos x - 3\,\cos \,\,2x + \cos \,3x$$           is

A. $$n\pi + \frac{\pi }{8}$$
B. $$\frac{{n\pi }}{2} + \frac{\pi }{8}$$
C. $${\left( { - 1} \right)^n}\frac{{n\pi }}{2} + \frac{\pi }{8}$$
D. $$2n\pi + {\cos ^{ - 1}}\frac{3}{2}$$
Releted Question 4

Number of solutions of the equation $$\tan x + \sec x = 2\cos x$$     lying in the interval $$\left[ {0,2\pi } \right]$$  is:

A. 0
B. 1
C. 2
D. 3

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