# Quick Trig. Question

1. Nov 8, 2011

### mrshappy0

1. The problem statement, all variables and given/known data
I am working through a calc 2 problem. I managed to get here without really completely understanding trig. There was a point in the problem where θ=Tan-1(-2/2) = -Pi/4. How does this work?

2. Relevant equations
I do not know any relevant equations

3. The attempt at a solution
I really have no clue. I have done research countless times.

2. Nov 8, 2011

### symbolipoint

For purposes of the Inverse Tangent, the Tangent function is restricted to the angle values from negative pi/2 to positive pi/2. A tangent of (-2/2) is the same as the tangent of (-1), and just relating this to the unit circle, this ange is -π/4.

3. Nov 8, 2011

### Staff: Mentor

I would advise you to spend some time reviewing basic trigonometry, especially in relation to the trig functions and their inverses. If you are trying to work through integrals without a solid understanding of trig, you will really have a hard time, particularly when it comes to trig substitutions.

Some time invested in reviewing your old precalc book would really pay off. Alternatively, there are many helpful videos about a variety of topics in math at khanacademy.org. A good place to start would be http://www.khanacademy.org/#trigonometry.