trig
posted by Anonymous .
Write the expression and evaluate. There is only one answer whIch should match the range of the inverse trig function.
Sec^1(2)
Sec^1(sqrt2)
Tan^1(sqrt3)
Tan^1(sqrt3)

I will do the 2nd one:
sec^1 (√2) = Ø , such that sec Ø = √2
or
cos Ø = 1/√2
I know that cos 45° = 1/√2
but the cosine is negative in II and III
so Ø = 18045° = 135°
or Ø = 180+45 = 225°
They probably expect the answer of 135° or 3π/4 radians 
How did you come up with 135 being the answer? I understand what you did but you said it could also be 225, so what makes you pick 135?

Also doesnt the cos45 = sqrt2/2 not 1/sqrt 2?

yes, because sqrt2/2 = 1/sqrt2