1. ## Trig question

Solve Sin2x=Cos2x

I know:

Sin2x=2SinxCosx

I also know:

Cos2x=cos²x-sin²x
Cos2x=2cos²x-1
Cos2x=1-2sin²x

How do I rearrange and solve?

Thanks x

2. Originally Posted by hymnseeker
Solve Sin2x=Cos2x

I know:

Sin2x=2SinxCosx

I also know:

Cos2x=cos²x-sin²x
Cos2x=2cos²x-1
Cos2x=1-2sin²x

How do I rearrange and solve?

Thanks x
sin2x=2sincosx is the double angle formula, which ones do you wish to solve?

3. Sorry, the question was:

Solve Sin2x=Cos2x

4. Originally Posted by hymnseeker
Sorry, the question was:

Solve Sin2x=Cos2x
Ok. Try using $\displaystyle SinA/CosA = TanA$

Then $\displaystyle Tan2x=1$ and $\displaystyle 2x = 45$degrees plus the solution in the third fifth and seventh quadrant

Does this help atol?

5. Thanks man.

Got it.

6. Originally Posted by hymnseeker
Thanks man.

Got it.

No problem, just make sure for these types of questions that you know
1.sine is positive in quads 1 and 2
2.cosine is positive in 1 and 4
3.tangent is positive in 1 and 3
4.sin0=sin180=0
5.cos90=cos270=0