Posted by **Anonymous** on Saturday, September 3, 2011 at 4:46pm.

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 -
**Reiny**, Saturday, September 3, 2011 at 8:25pm
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°

They probably expect the answer of 135° or 3π/4 radians

- trig -
**Anonymous**, Sunday, September 4, 2011 at 1:56pm
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 -
**Charles**, Sunday, September 4, 2011 at 2:17pm
Also doesnt the cos45 = sqrt2/2 not 1/sqrt 2?

- trig -
**Steve**, Wednesday, September 21, 2011 at 1:14pm
yes, because sqrt2/2 = 1/sqrt2

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