(i) In an isosceles triangle the angles are in the ratio 7 : 4 : 7. Find each base angle of the triangle.

(ii) Find the angles of an isosceles triangle, if the ratio of the base angle to the vertical angle 2 : 5.

ABC is an equilateral triangle. If AD bisects angle A, prove that AD is perpendicular bisector of BC.

Two sides of a triangle are 8 cm and 11 cm, The length of its third side lies between a cm b cm, find the values of a and b if a < b.