# Homework Help: Tangent sum or difference

1. Mar 6, 2010

### big billy

I am trying to find the exact value for tan(15). I figure my equation as 40 - 30 to give the 15.

when deriving my equation is where I have the problem. can anyone help please.

(1-√(3)/3)/(1 + 1 * √(3)/3)

2. Mar 6, 2010

### vela

Staff Emeritus
Looks good so far. To rationalize the denominator, multiply the top and bottom by (1-√(3)/3).

3. Mar 6, 2010

### Sweet_GirL

$$40-30 \neq 15$$

I think you mean $$45-30$$