Hint: Make a sketch of an isosceles triangle with two of its sides and angles angles. : PQ (r) = PR (q) = 8cm : R^\circ = Q^\circ = 30^\circ Sum of angles in a triangle = 180^\circ P^\circ + Q^\circ + R^\circ = 180^\circ P^\circ + 30^\circ + 30^\circ = 180^\circ P^\circ = 180^\circ - 60^\circ p^\circ = 120^\circ. : PQ = r, PR = q, QR = p Using sine rule: \(\frac{p}{sinP}\) = \(\frac{q}{sinq}\) \(\frac{p}{sin120^\circ}\) = \(\frac{8}{sin30^\circ}\) cross multiply p = \(\frac{8 X sin120^\circ}{sin30^\circ}\) p = \(\frac{8 X \sqrt3/2 }{1/2}\) p = 8\sqrt3