The general value of X in the equation 2sin2x= sinx is:
a.nPie+Pie/2 b.npie/4 c. 2npi+pie/2

Question

The general value of X in the equation 2sin2x= sinx is: 
a.nPie+Pie/2      b.npie/4  c. 2npi+pie/2

hartnn · Answer

use sin2x =2sin x cos x 

something gets cancelled out, what ?

anonymous · Answer

and then? 4sinx cosx = sinx 
          4cosx=1
 and then?

hartnn · Answer

be careful, 
you will consider sin x =0 too

4 sin x cos x = sin x
----> sin x (4cos x-1) = 0
sin x =0 or 4 cosx-1 =0

got this ?

anonymous · Answer

2sinxcosx=sinx
2cosx=1
cosx=1/2
npi+-pi/6

anonymous · Answer

theres 2sin2x ..??? not only sin2x

hartnn · Answer

can you solve 4cos x-1 = 0 ?

anonymous · Answer

yeahh

hartnn · Answer

well, but with that, you would not get any choice as your answer....because 1/4 is not the cos value of any standard angle...

hartnn · Answer

you sure the Q is correct ?

anonymous · Answer

yeah it was in a book

debbieg · Answer

Yeah, that factor of 2 in front is definitely a sticky widget here!

@rajatgang , be careful, you can NOT divide through by sin(x) in this equation!! Must set is all = 0 and factor. Never divide by an unknown that might be =0.

anonymous · Answer

im trying it....

anonymous · Answer

i guess question is wrong ....

debbieg · Answer

With those as the answer choices? Hmm. Well, books have been known to have errors in them. I dunno, this doesn't look right, and you can punch it into Wolfram and see that none of those are the complete solution set.

debbieg · Answer

2sin(2x)= sinx

Even if you remove the 2 in front on the LHS, you don't get any of those as the complete solution set.

anonymous · Answer

Here is a step by step solution: http://www.symbolab.com/solutions/trigonometric_equations?query=2sin2x%3D%20sinx