How are isosceles triangles and scalene triangles in common?

Answer 1

-- both types of triangle are plane (2-dimensional) figures

-- both types of triangle have three sides

-- both types of triangle have three interior angles that add up to 180 degrees

-- in both types of triangle, sin(A)/a = sin(B)/b = sin(C)/c

Those are the only characteristics shared by isosceles and scalene triangles.