# Thread: Can I have some help with this trig equation?

1. ## Can I have some help with this trig equation?

Hi all

Im kind of stuck on where to go with this trig equation:

$\displaystyle 5 sin 3x = 7 cos 3x$

I was thinking maybe divide by $\displaystyle 7 cos 3x$to make it look like $\displaystyle \frac{5 sin 3x}{7 cos 3x}$$\displaystyle = tan x Im really stuck on where to go Any help is greatly appreciated. Thanks 2. Originally Posted by fishkeeper Hi all Im kind of stuck on where to go with this trig equation: \displaystyle 5 sin 3x = 7 cos 3x I was thinking maybe divide by \displaystyle 7 cos 3x to make it look like \displaystyle \frac{5 sin 3x}{7 cos 3x}$$\displaystyle = tan x$

Im really stuck on where to go

Any help is greatly appreciated.

Thanks
$\displaystyle 5 sin 3x = 7 cos 3x \implies \frac{sin3x}{cos3x} = \frac{7}{5} \implies tan3x = \frac{7}{5}$

can you find x now?

3. Thankyou Harish, I cans ee what you have done which is most useful.

It seems so simple once its written down in front of you haha, but I am pretty sure I've learned from this, and if it came up in the exam I could answer a question like this which is the main thing!

thanks again