ABCD is a cyclic quadrilateral (see Fig. 3.7). Find the angles of the cyclic quadrilateral.
We know that the opposite angles of a cyclic quadrilateral are supplementary, therefore,
∠A + ∠C = 180°
⇒ 4y + 20 + 4x = 480°
⇒ 4x + 4y = 60°
⇒ x + y = 40° ...(i)
[Dividing throughout by 4]
and ∠B + ∠D = 180°
⇒3y - 5 + 7x + 5= 180°
⇒ 7x + 3y = 180° ...(ii)
From equation (i), we have
y = 40 - x ...(iii)
Substituting this value of y in equation (ii), we get
7x + 3(40 - x) = 180°
⇒7x + 120 - 3x = 180°
⇒ 4x = 60
Substituting x = 15 in equation (iii), we get
y = 40 - x
= 40 - 15 = 25°
Hence, required angles be
∠A = 4y + 20 = 4 × 25 + 20 = 120
∠B = 3y - 5 = 3 × 25 - 5 = 75 - 5 = 70
∠C = 4x = 4 × 15 = 60°
∠D = 7x + 5 = 7 × 15 + 5
= 105 + 5 = 110°
Find the number of solutions of the follow ing pair of linear equations :
x + 2y - 8 = 0
2x + 4y = 16