can someone please explain how to do this?

Find all exact solutions on the interval [0, 2π). Look for opportunities to use trigonometric identities. (Enter your answers as a comma-separated list. If an answer does not exist, enter DNE.)
sin²(x) - cos²(x) - sin²(x) = 0
x =

x =pi/2,3pi/2

Step-by-step explanation:

sin²(x) - cos²(x) - sin²(x) = 0

Simplify

sin²(x)  - sin²(x) = 0

Leaving us with

- cos²(x)  = 0

Divide each side by -1

- cos²(x/-1  = 0/-1

 cos²(x)  = 0

Take the square root of each side

sqrt( cos²(x))  = sqrt(0)

 cos(x)  = 0

Taking the inverse cos of each side

cos^-1(cos(x))  = cos^-1(0)

x = pi/2     x = 3pi/2

x = π/2, 3π/2

Step-by-step explanation:

sin²(x) - cos²(x) - sin²(x) = 0

-cos²(x) = 0

cos²(x) = 0

cos(x) = 0

x = π/2, 3π/2

step-by-step explanation: