The angles A, B, C and D of a quadrilateral have measures in the ratio 2 : 4 : 5 : 7. Find the measures of these angles. What type of quadrilateral is it? Give reasons.
In the figure, ABCD is a parallelogram in which AB is produced to E so that AB = BE
(a) Prove that ED bisects BC
(b) If AD = 10 cm, find OB.
(iii) PQ || AC | From (ii)
SR || AC | From (i)
∴ PQ || SR
| Two lines parallel to the same line are parallel to each other
Also, PQ = SR | From (ii)
∴ PQRS is a parallelogram.
| A quadrilateral is a parallelogram if a pair of opposite sides are parallel and are of equal length