... If the lengths of two sides of an isosceles triangle are and 20, what is the perimeter of the triangle? 23 If the integer lengths of the three sides of a triangle are 5, x, and 10, what is the ... equilateral, so AC ෆෆ = 10 Angles BDE and BED each measure 60 + 15 = 75°, since they are exterior angles of triangles ADB and CEB Therefore, triangles ADB and CEB have the same shape and size, so ෆෆ = ... square has four angles that are 90° each, as does a rectangle and cube The angles inside a triangle add up to 180°, and one angle in a right triangle is 90°, so the other two add up to 90°, so there...