Question

The point (3, -4) is on the terminal side of an angle theta. What is cos theta?

Answer 1

The point (3, -4) lies in the quadrant 4. 

The length of the vector will be = $\sqrt{(3)^{2} +(4)^{2} } =5$

cos theta can be found by dividing the horizontal component of the vector (which is 3) with the length of the vector.

So,

$cos(theta)= \frac{3}{5}$