i am converting degrees to rad and the degree is 30

You need to use the degree to radian ratio. The ratio is 

$${\frac{{\mathtt{\pi}}}{{\mathtt{180}}}} = {\frac{{\mathtt{radians}}}{{\mathtt{degrees}}}}$$

So just plug in the degree, and solve!

$${\frac{{\mathtt{\pi}}}{{\mathtt{180}}}} = {\frac{{\mathtt{rad}}}{{\mathtt{30}}}}$$

$${\mathtt{rad}} = {\frac{{\mathtt{30}}{\mathtt{\,\times\,}}{\mathtt{\pi}}}{{\mathtt{180}}}}$$

30 degrees in radians is pi/6 radians :)