How do I find the median for a congruent triangle

The length of a median is equal to half the square root of the difference of twice the sum of the squares of the two sides of the triangle that include the vertex the mediam is drawn from and the square of the side of the triangle the median is drawn to.

triangle sides by a, b, c.

ma=122c2+2b2-a2

mb=122c2+2a2-b2

mc=122a2+2b2-c2