# Thread: sin x=5/13 tan x=-5/12 ;x=?

1. ## sin x=5/13 tan x=-5/12 ;x=?

sin x=5/13 tan x=-5/12 ;x=?

2. Hint:
If sin x is positive, then x can be in the 1st and 4th quadrants. If tan x is negative, x can be in the 2nd and 4th quadrants.

3. Originally Posted by wingless
Hint:
If sin x is positive, then x can be in the 1st and 4th quadrants. If tan x is negative, x can be in the 2nd and 4th quadrants.
correction
sin x is positive, then x can be in the 1st and 2nd quadrants

4. True, I counted the quadrants clockwise

5. Originally Posted by gateway
$\sin x=\frac{5}{13} \ \ \tan x=-\frac{5}{12} \ \ x=?$
You're looking for an angle whose terminal side is in the second quadrant, since that's the quadrant where Sin is positive and Tan is negative.

$\theta=\arcsin\left(\frac{5}{13}\right)\approx22.6 ^\circ$

The reference angle in the 2nd quadrant is $22.6^\circ$

For any angle $\theta, \ \ 0 < \theta < 180^\circ$, its reference angle is defined as $180^\circ - \theta$

$\theta = 180^\circ - 22.6^\circ \approx 157.4^\circ$