Formula issue imputing Trig

hello everyone. Needing help with correct formula for calculating the opposite side of an Isosceles Triangle. Given that Cell A1 is the Angle between the congruent sides. and B1 is the length of each Congruent Side. C1 is the result(length) of opposite side. My formula result in C1 keeps coming up to 0. but checking with calculator and online triangle calculator it, I should be getting a number.
Values
A1=15
B1=30
expected result in C1=7.83157


C1(formula)=SQRT((((B1*B1)+(B1*B1))-(2*(B1*B1)))*(COS(A1)))

*This formula is based off online Triangle Calculator formula. I dont know how to Square a #on excel, so i just multiplied a cell by itself. Im pretty sure this isnt a trig problem its more of a "im not putting it into excel properly" any help would be great.
Thanks in advance

[QUOTE=JohnTopley;5603009]This

=SQRT(B1^2+B1^2-(2*B1^2*COS(RADIANS(A1))))

^^ that was it!!!! Thanks for the info. i'm now a little smarter.

thank you for the info on exponets. that helped