Prove that the diagonals of an isosceles trapezium are equal.
State, true or false : (i) Two similar polygons are necessarily congruent. (ii) Two congruent polygons are necessarily similar. (iii) All equiangular triangles are similar. (iv) All isosceles triangles are similar. (v) Two isosceles-right triangles are similar. (vi) Two isosceles triangles are similar if an angle of one is congruent to the corresponding angle of the other. (vii) The diagonals of a trapezium divide each other into proportional segments.