1)Oh this. for sin (3θ) = -1 , you 1st bring sin over to -1 ... so you'll get a basic angle of π/2 ..
since its -1, 3θ will lie in 3rd or 4th quadrant . and you get the angles (within the range below) of there and divide by 3 to get θ.
Oh btw, change the range to 0 ≤ 3θ < 6π as you'll be working with 3θ instead of θ .
2) For sec (3θ/2) = -2 ... since sec is 1/cos , you flip the whole equation (if you understand) and it'll become cos(3θ/2) = -1/2 , so the basic angle will be π/3 . and since it's -1/2 , 3θ/2 will lie in 2nd and 3rd quadrant . get the angles (within the range below) and multiply it by 2/3 . to get θ.
Range: 0 ≤ 3θ/2 < 3π
