42.9866=3.14*r^2

Solution for 42.9866=3.14*r^2 equation:

Simplifying
42.9866 = 3.14r2

Solving
42.9866 = 3.14r2

Solving for variable 'r'.

Move all terms containing r to the left, all other terms to the right.

Add '-3.14r2' to each side of the equation.
42.9866 + -3.14r2 = 3.14r2 + -3.14r2

Combine like terms: 3.14r2 + -3.14r2 = 0.00
42.9866 + -3.14r2 = 0.00

Add '-42.9866' to each side of the equation.
42.9866 + -42.9866 + -3.14r2 = 0.00 + -42.9866

Combine like terms: 42.9866 + -42.9866 = 0.0000
0.0000 + -3.14r2 = 0.00 + -42.9866
-3.14r2 = 0.00 + -42.9866

Combine like terms: 0.00 + -42.9866 = -42.9866
-3.14r2 = -42.9866

Divide each side by '-3.14'.
r2 = 13.69

Simplifying
r2 = 13.69

Take the square root of each side:
r = {-3.7, 3.7}