The terminal ray of angle β , drawn in standard position, passes through the point (−4, 3√5) . What is the value of cosβ ? Enter your answer, in simplest radical form, in the box
The point -4 , 3 sqrt5 forms a right triangle with the x axis in the 2nd quadrant ( so cos will be NEGATIVE)
find the hypotenuse of this right triangle
(-4)^2 +(3 sqrt5)^2 = hyp ^2
16 + 45 = hyp^2
sqrt 61 = hyp
Now cos = adj/hyp = - 4 / sqrt 61 = -4 sqrt61 / 61
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