help@askiitians.com

1800-150-456-789

Trigonometry> solve for x sin3x sin(cube) x +cos3x co...

question mark

solve for xsin3x sin(cube) x +cos3x cos(cube) x=0arun sir answered me but it was a tough method i need some easy way as i am in 11th so a method which i couldget please answer>>>

rashmi , 10 Years ago

Grade 11

2 Answers

Jitender Singh

Last Activity: 10 Years ago

Ans:
$sin3x.sin^{3}x + cos3x.cos^{3}x = 0$
$sin3x.sin^{3}x = -cos3x.cos^{3}x$
$tan3x = \frac{-1}{tan^{3}x}$
$\frac{3tanx-tan^{3}x}{1-3tan^{2}x} = \frac{-1}{tan^{3}x}$
$3tan^{4}x-tan^{6}x = -1+3tan^{2}x$
$tan^{6}x -3tan^{4}x + 3tan^{2}x -1 = 0$

It is a simple polynomial, you can easily solve. And if you have options, you can hit & trial.
$tan^{6}x - 1 = 3tan^{4}x - 3tan^{2}x$
$(tan^{3}x - 1)(tan^{3}x + 1) = 3tan^{2}x(tan^{2}x-1)$
$tanx = \pm 1$
$x = n\pi \pm \frac{\pi }{4}$

rashmi

Last Activity: 10 Years ago

sir can u explain me how u solved the third last step not getting ?? is there any such identity??

Provide a better Answer & Earn Cool Goodies

Enter text here...

LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

Full Live Access

Study Material

Live Doubts Solving

Daily Class Assignments

Ask a Doubt

Get your questions answered by the expert for free

Enter text here...

question mark

In ABC, if cot A+cot B+cot C = cosecA cosecB cosecC, then prove that ABC is right angle triangle.

Trigonometry

1 Answer Available

Last Activity: 2 Year ago(s)

question mark

\tFind the general solution of equation tan3∂=cot2∂For all angles between -720 and +720

Trigonometry

0 Answer Available

Last Activity: 2 Year ago(s)

question mark

To prove : Cosec(45 degree - A)Cosec(45 degree + A) = 2SecA

Trigonometry

0 Answer Available

Last Activity: 2 Year ago(s)

question mark

cos^2 13ºcos^2 47º+cos^2 73º =? …..................

Trigonometry

0 Answer Available

Last Activity: 2 Year ago(s)

question mark

Derive a formula for the area of the triangle, given b, A, B, and C. That is, derive the formula: (b^2sinAsinC)/(2sinB)

Trigonometry

0 Answer Available

Last Activity: 2 Year ago(s)

View all Questions