58=r*r*3.14*.5

Solution for 58=r*r*3.14*.5 equation:

Simplifying
58 = r * r * 3.14 * 0.5

Reorder the terms for easier multiplication:
58 = 3.14 * 0.5r * r

Multiply 3.14 * 0.5
58 = 1.57r * r

Multiply r * r
58 = 1.57r2

Solving
58 = 1.57r2

Solving for variable 'r'.

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

Add '-1.57r2' to each side of the equation.
58 + -1.57r2 = 1.57r2 + -1.57r2

Combine like terms: 1.57r2 + -1.57r2 = 0.00
58 + -1.57r2 = 0.00

Add '-58' to each side of the equation.
58 + -58 + -1.57r2 = 0.00 + -58

Combine like terms: 58 + -58 = 0
0 + -1.57r2 = 0.00 + -58
-1.57r2 = 0.00 + -58

Combine like terms: 0.00 + -58 = -58
-1.57r2 = -58

Divide each side by '-1.57'.
r2 = 36.94267516

Simplifying
r2 = 36.94267516

Take the square root of each side:
r = {-6.078048631, 6.078048631}