Problem: what is the measure of the radius of the circle inscribed in a triangle whose sides measure 8 , 15 and 21 units ?
Rationale: "sides are 8 , 15 and 21 . . . thus it is right angle triangle since 21 ^ 2 = 8 ^ 2 + 15 ^ 2 therefore , area = 1 / 2 * 15 * 8 = 60 we have to find in - radius therefore , area of triangle = s * r . . . . where s = semi - perimeter and r = in - radius now s = semi - perimeter = 21 + 15 + 8 / 2 = 22 thus , 60 = 22 * r and hence r = in - radius = 2.6 option b"
annotated_formula: divide(triangle_area_three_edges(8, 15, 21), divide(triangle_perimeter(8, 15, 21), const_2))