cos^2(x-pi/4)-3cosx=1

Question

anonymous · Answer

@kirin  what do we need to find here?

anonymous · Answer

find x

anonymous · Answer

i think we need to solve 
$$\cos^2(x-\frac{ \pi }{ 4 })$$ first
we will use this formula cos(A-B) = cosA cosB +sinA sinB

anonymous · Answer

can you send answer ?

anonymous · Answer

sorry previous approach was wrong
we are going to use half angle formulae
cos2x = 2*cos^2x-1 it surely gonna give u an answer

Sorry i cannot give direct answer here

anonymous · Answer

@kirin  we can work step by step
u just need to solve with me here

dumbcow · Answer

@niksva , does that approach give an exact answer? im not seeing it, this seems to have an numerical approximation solution

anonymous · Answer

This post is too difficult for me.I still do not solve it

anonymous · Answer

yeah it is not giving an exact answer
we need to look at other way of solving this problem @dumbcow  @kirin
do u have any other idea @dumbcow ?

dumbcow · Answer

@kirin , is this calculus class?

anonymous · Answer

yes. this is my test

dumbcow · Answer

ok you can approximate using newtons method

anonymous · Answer

i will try

dumbcow · Answer

$$x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}$$
use
$$f(x) = \sin(2x) -6\cos(x) -1$$

anonymous · Answer

@dumbcow  r u suggesting newton raphson method here?

dumbcow · Answer

yes his approximation method for finding zeros

anonymous · Answer

this ques looks complicated

anonymous · Answer

The solutions to this are not nice at all

anonymous · Answer

yeahh it seems one has to play with numbers over here  :)

anonymous · Answer

the solutions are irrational

dumbcow · Answer

there are 2 solutions within domain 0<x<2pi

dumbcow · Answer

http://www.wolframalpha.com/input/?i=cos%28x-%28pi%2F4%29%29%5E2+-3cos%28x%29+%3D+1+for+x%3D0+to+2pi