# Thread: Find the value of...

1. ## Find the value of...

I am having trouble reviewing trig. I can't remember how to find function values for the trig functions byn hand, unless the angle is 30,45,60 etc. How do I determine cot(135 degrees) ?

I am having trouble reviewing trig. I can't remember how to find function values for the trig functions byn hand, unless the angle is 30,45,60 etc. How do I determine cot(135 degrees) ?
Draw a unit circle. The reference angle is 45 degrees and the cot function is negative in the second quadrant. cot(135 degrees) = - cot(45 degrees).

I am having trouble reviewing trig. I can't remember how to find function values for the trig functions byn hand, unless the angle is 30,45,60 etc. How do I determine cot(135 degrees) ?
135 degrees is 45 degrees above the negative x-axis in quad II

I am having trouble reviewing trig. I can't remember how to find function values for the trig functions byn hand, unless the angle is 30,45,60 etc. How do I determine cot(135 degrees) ?
Niether can anyone else; without some identities that is...

135?

You must recognize that this is simply a 45 degree angle when refrenced to the x axis...

Also, $tan45^\circ=cot45^\circ=1$ because ${sinx}={cosx}$ at $x=45^\circ$, and since $tanx=\frac{sinx}{cosx}$...

Then, since $135^\circ$ is in quadrant two, you can conclude that the answer will be negative.

Here, check it out...

http://en.wikipedia.org/wiki/List_of...ric_identities