To find the value of cosθ, we can use the coordinates of the point on the terminal side of the angle in standard position. Since the coordinates of the point on the terminal side are (21,20), we can use the formula for the cosine of an angle in standard position:
cos θ = x / r
where x is the x-coordinate of the point on the terminal side of the angle and r is the distance from the origin to this point. In this case, the x-coordinate of the point is 21 and the distance from the origin to the point is sqrt(21^2 + 20^2) = sqrt(441 + 400) = sqrt(841) = 29.
Substituting these values into the formula for cos θ, we get:
cos θ = 21 / 29
To find the exact value of cos θ in simplest radical form, we need to simplify this fraction. Dividing the numerator and denominator by their greatest common divisor, we get:
cos θ = (21 / 29) / (1 / 29) = 7 / 1 = 7
Therefore, the exact value of cos θ in simplest radical form is 7.