# Math Help - combining powers with trigonometry functions

1. ## combining powers with trigonometry functions

Hi

A solution to a problem i have is;

x^4.sinx+4x^3.cosx

does this simplfy to

sinx^5 + 12cosx^4

John

2. ## Re: combining powers with trigonometry functions

Originally Posted by celtic1234
Hi

A solution to a problem i have is;

x^4.sinx+4x^3.cosx

does this simplfy to

sinx^5 + 12cosx^4

John
No, because $x^4$ and $\sin x$ are two completely different functions; thus, it's a no-no to carry the $x^4$ term inside the sine function. To avoid such confusion, I would write it like $x^4\sin(x)+4x^3\cos(x)$.

3. ## Re: combining powers with trigonometry functions

thank you
this site is a god send.
John

4. ## Re: combining powers with trigonometry functions

You could simplify this by taking out a common factor though.

$\displaystyle x^4\sin{(x)} + 4x^3\cos{(x)} = x^3\left[x\sin{(x)} + 4\cos{(x)}\right]$