Question

class 9 maths chapter7 ex 7.2 solution​

Answer 1

Step-by-step explanation:

it is all about replacing the zero of the polynomial

Answer 2

AB = AC [Given] …(1)

AB = AD [Given] …(2)

From (1) and (2), we have

AC = AD

Now, in ∆ABC, we have

∠ABC + ∠ACB + ∠BAC = 180° [Angle sum property of a A]

⇒ 2∠ACB + ∠BAC = 180° …(3)

[∠ABC = ∠ACB (Angles opposite to equal sides of a A are equal)]

Similarly, in ∆ACD,

∠ADC + ∠ACD + ∠CAD = 180°

⇒ 2∠ACD + ∠CAD = 180° …(4)

[∠ADC = ∠ACD (Angles opposite to equal sides of a A are equal)]

Adding (3) and (4), we have

2∠ACB + ∠BAC + 2 ∠ACD + ∠CAD = 180° +180°

⇒ 2[∠ACB + ∠ACD] + [∠BAC + ∠CAD] = 360°

⇒ 2∠BCD +180° = 360° [∠BAC and ∠CAD form a linear pair]

⇒ 2∠BCD = 360° – 180° = 180°

⇒ ∠BCD = 180°/2 = 90°

Thus, ∠BCD = 90°