Hi Guys,

I am trying to investigate a function, during the process I need to solve this equation:

sin(x)+cos(2x)=0

in the region 0<=x<=2*Pai

How do I solve it ?

thanks !

Printable View

- Mar 5th 2011, 07:23 AMWeeGhow to solve this equation ?
Hi Guys,

I am trying to investigate a function, during the process I need to solve this equation:

sin(x)+cos(2x)=0

in the region 0<=x<=2*Pai

How do I solve it ?

thanks ! - Mar 5th 2011, 07:25 AMProve It
Use the identity to turn your equation into a quadratic, which you can then solve.

- Mar 5th 2011, 07:34 AMTheCoffeeMachine
Start by writing it as and recall that .

So we have . You should be able to solve it with ease now.

**Hint:**if then (where is an integer, or zero). - Mar 5th 2011, 08:11 AMWeeG
I used the quadratic idea, I did t=sin(x)

and got t1=-0.5 and t2=1

thus, I got:

sin(x)=-0.5 and sin(x)=1 my solution is x=pai/2 and x=11/6*pai

but there should be another one at x=3.63, I have no idea why.... - Mar 5th 2011, 08:31 AMskeeter