# trig

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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)

• trig -

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 = 180-45° = 135°
or Ø = 180+45 = 225°

• trig -

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?

• trig -

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

• trig -

yes, because sqrt2/2 = 1/sqrt2

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