Mathematics
Find x :

Triangles
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Answer
In △ ADC,

⇒ AC = AD (Given)
⇒ ∠ACD = ∠ADC = 42° (Angles opposite to equal sides are equal)
By angle sum property of triangle,
⇒ ∠ACD + ∠ADC + ∠CAD = 180°
⇒ 42° + 42° + ∠CAD = 180°
⇒ ∠CAD + 84° = 180°
⇒ ∠CAD = 180° - 84° = 96°.
Since, BCD is a straight line.
From figure,
⇒ ∠ACD + ∠ACB = 180°
⇒ 42° + ∠ACB = 180°
⇒ ∠ACB = 180° - 42° = 138°.
In △ ABC,
⇒ AC = BC (Given)
⇒ ∠ABC = ∠CAB = z (let) (Angles opposite to equal sides are equal)
By angle sum property of triangle,
⇒ ∠ABC + ∠CAB + ∠ACB = 180°
⇒ z + z + 138° = 180°
⇒ 2z + 138° = 180°
⇒ 2z = 180° - 138°
⇒ 2z = 42°
⇒ z = = 21°.
⇒ ∠ABC = ∠CAB = 21°.
Since, EAD is a straight line.
From figure,
⇒ ∠EAB + ∠CAB + ∠CAD = 180°
⇒ x + 21° + 96° = 180°
⇒ x + 117° = 180°
⇒ x = 180° - 117° = 63°.
Hence, x = 63°.
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