6. (a) In the given figure, O is the centre of the circle and ∠PBA= 45°. Calculate the value of ∠PQB.   7. (b) In an equilateral ΔABC of side 14 cm, side BC is the diameter of a semi-circle as shown in the figure below. Find the area of the shaded region. (Take π = 22/7 and √3 = 1.732)   8. (c) If x = √a + 3b + √a − 3b √a + 3b − √a − 3b , prove that 3bx2 − 2ax + 3b = 0