Inverse Trig Functions (1 Viewer)

[Brad_Mclain]

Ok heres the Question:

Evaluate the following angles in terms of pi

sin-1(-3/2)

I get 5pi/3 for my answer but the textbook says -pi/3

Can someone explain to me what i am doing wrong?

Note: For anyone who has Jones and Couchman textbook, it is Book 2, Page 197, EX 27.3, 1 (c).

 

[airie]

Uhh...isn't 5pi/3 and -pi/3 the same thing? o.0

 

[airie]

On second thoughts...check what's the range that the question wants. Is it between 0 to 2pi or between -pi to pi? If it's the latter, then you should convert your solution into a value in that range and hence the answer

 

[Brad_Mclain]

The question specified no range but the range for sin-1 is pi/2 to -pi/2

so does this mean they are the same thing?

How should i write my answers?

 

[Riviet]

The question specified no range but the range for sin-1 is pi/2 to -pi/2

so does this mean they are the same thing?

How should i write my answers?

5pi/3 is the same thing as -pi/3, but 5pi/3 is not between -pi/2 and pi/2, so you need to convert your angle so that it is in the range. Therefore you subtract 2pi from 5pi/3 to get -pi/3.

 

[Brad_Mclain]

Thankyou for that clarification, back to do some more questions!

 

[followme]

Sin-1 (-x) = - sin-1(x) so: sin-1 (-root3/2) = - sin-1 (root3/2) = -pi/3