Find the distance between these two polar points

P1(1.3,-47 degrees) and P2(-3.6,-62 degrees)

I know the formula to find distance is

square root R1^2+R2^2-2(R1R2)cos(angle 2- angle1)

But when I plug in the numbers in my calculator I get an unreal answer but checking the answer on the back of my math book I know that is incorrect.

Can anyone show me how to do this problem?