d = √ a * b + c²
h = 1/2 * √ 4c² - ( a - b )²
m = ( a + b ) / 2
rc = c * √ ( a * b + c² ) / ( 4c² - ( a - b )² )
g = ( a - b ) / 2
p = a + b + 2 * c
A = 1/4 * √ ( a + b )² * ( a - b + 2c ) * ( b - a + 2c ) = m * h
α = arccos( ( g² + c² - h² ) / ( 2 * g * c ) )
β = 180° - α
