Question

Given this unit circle, what is

the value of x?
(x,-√2)
X =
(1,0)
[?]
Enter

Answer 1

x = - √2/2

Explanation:

We know that x = rcosθ and y = rsinθ. The unit circle always have radius of 1 unit. Therefore, r = 1 as defined. Hence:

x = cosθ, y = sinθ

x = cosθ, θ = arcsin(y)

x = cos{arcsin(-√2/2)}

Find the measurement or θ that makes sinθ = -√2/2 and that is π + π/4 = 5π/4.

x = cos(5π/4)

And cos(5π/4) = - √2/2 as well. Hence, x = - √2/2.