Question

What is the exact value of cos-1(-1/sqrt2)

Answer 1

In what quadrants Cosine is -ve?
2nd and 3rd

Answer 2

let x = cos-1(-1/sqrt2)
cos(x) = (-1/sqrt2)
now we know x is either in 2nd or in 3rd quadrants

Answer 3

cos 45 = 1/sqrt2
Sry abt the 3rd Quadrant..cosine is -ve in 2nd quadrant

Answer 4

so, reference angle is 45
180-45 =135
x= 135 degrees