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In the given figure, side CA of △ABC has been produced to E. If AC = AD = BD; ∠ACD = 46° and ∠BAE = x°; find the value of x.

In the given figure, side CA of △ABC has been produced to E. If AC = AD = BD; ∠ACD = 46° and ∠BAE = x°; find the value of x. R.S. Aggarwal Mathematics Solutions ICSE Class 9.

Triangles

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Answer

Given,

AD = AC

In △ADC,

⇒ ∠ACD = ∠ADC = 46° (Angles opposite to equal sides in a triangle are equal)

By angle sum property of triangle,

⇒ ∠ACD + ∠ADC + ∠CAD = 180°

⇒ 46° + 46° + ∠CAD = 180°

⇒ 92° + ∠CAD = 180°

⇒ ∠CAD = 180° - 92°

⇒ ∠CAD = 88°.

From figure,

⇒ ∠ADB + ∠ADC = 180° (Linear pair)

⇒ ∠ADB + 46° = 180°

⇒ ∠ADB = 180° - 46°

⇒ ∠ADB = 134°.

In △ABD,

AD = BD

⇒ ∠DAB = ∠DBA = z (let) (Angles opposite to equal sides are equal)

By angle sum property of triangle,

⇒ ∠ADB + ∠DAB + ∠DBA = 180°

⇒ 134° + z + z = 180°

⇒ 2z = 180° - 134°

⇒ 2z = 46°

⇒ z = 46°2\dfrac{46°}{2}

⇒ z = 23°.

⇒ ∠DAB = ∠DBA = 23°

From figure,

⇒ ∠CAD + ∠DAB + ∠BAE = 180° (Linear pair)

⇒ 88° + 23° + x° = 180°

⇒ 111° + x° = 180°

⇒ x° = 180° - 111°

⇒ x° = 69°

⇒ x = 69.

Hence, the value of x = 69.

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