1. ## Trigs

how do i solve this? i'm suppose for solve x
(Cotx)(Cosx)= Cosx

2. Originally Posted by imthatgirl
how do i solve this? i'm suppose for solve x
(Cotx)(Cosx)= Cosx
$\displaystyle cot(x)~cos(x) = cos(x)$

$\displaystyle cot(x)~cos(x) - cos(x) = 0$

$\displaystyle (cot(x) - 1)~cos(x) = 0$

So either
$\displaystyle cot(x) - 1 = 0 \implies tan(x) = 1 \implies x = \frac{\pi}{4}, \frac{5\pi}{4}$

or
$\displaystyle cos(x) = 0 \implies x = \frac{\pi}{2}, \frac{3\pi}{2}$

-Dan

3. Thanks so much it was really helpful

4Sin(x)tan(x)-3tan(x)+20sin(x)-15

4. Originally Posted by imthatgirl
Thanks so much it was really helpful

4Sin(x)tan(x)-3tan(x)+20sin(x)-15
umm...i suppose you just want us to factor this.

tan(x) is common to the first two terms, 5 is common to the last two, so pull those out, we get:

$\displaystyle \tan x (4 \sin x - 3) + 5 (4 \sin x - 3)$

now the 4sin(x) - 3 is common to both terms, so pull that out, we get:

$\displaystyle (4 \sin x - 3)( \tan x + 5)$

and we're done

Aside: post new questions in a new thread