Question

An angle in standard position on a unit circle measures 2pi/5 radians. what are the exact coordinates of where the terminal side intersects the unit circle?

Thank you!

Answer 1

(x, y) = (cos(2π/5), sin(2π/5)) = ((1/4)(-1 + √5), (1/4)(2√5 + 2))

Explanation:

In standard position, the initial side of an angle lies on the positive x-axis, and the terminal side rotates counterclockwise from the initial side.

Since the angle measures 2π/5 radians, we need to find the point on the unit circle that is π/5 radians past the positive x-axis.

Let (x, y) be the coordinates of the point on the unit circle where the terminal side intersects. We can use the following trigonometric identities to find the values of x and y:

cos(2π/5) = x

sin(2π/5) = y

These values can be determined using either a calculator or the unit circle. Alternatively, we can use the fact that the angle 2π/5 is a special angle and can be expressed exactly in terms of square roots:

cos(2π/5) = (1/4)(-1 + √5)

sin(2π/5) = (1/4)(2√5 + 2)

Therefore, the exact coordinates of the point where the terminal side intersects the unit circle are

(x, y) = (cos(2π/5), sin(2π/5)) = ((1/4)(-1 + √5), (1/4)(2√5 + 2))