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. Cosβ = ?
(- 4, 3√5) = ( -4, √45) = (x , y)
cos B = x / r
r = √ [(-4)^2 + (√45)^2 ] = √ [ 16 + 45 ] = √61
So
cos B = -4/√61 = -4√61 / 61
