

It can be observed that, x + y + z + w then prove that AOB is a line.
\(⇒\)\(\text{ x+y+w+z = 360°}\)
It is given that,
\(\text{x+y = w+z}\)
So, (x + y) +(x + y) = 360°
2(x + y) = 360°
∴ (x + y) = 180°
Since x and y form a linear pair, AOB is a line.



(i) The kind of person the doctor is (money, possessions)
(ii) The kind of person he wants to be (appearance, ambition)
ABCD is a quadrilateral in which AD = BC and ∠ DAB = ∠ CBA (see Fig. 7.17). Prove that
(i) ∆ ABD ≅ ∆ BAC
(ii) BD = AC
(iii) ∠ ABD = ∠ BAC.
