In the given figure, AB divides ∆DAC in the ratio 1:3 and AB = DB. The value of x is
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Step-by-step explanation:
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Answer:
The value of x is 90°.
Step-by-step explanation:
We are given that AB divides ∠ DAC in the ratio 1 : 3 and AB is equal to DB.
We have to determine the value of x.
As it is given in the question that AB divides ∠ DAC in the ratio 1 : 3, that means; ∠DAB/∠BAC = 1/3
∠BAC= 3∠DAB
Let ∠DAB = y, then the value of ∠BAC = 3y ------------- [equation 1]
Now, after observing the figure, it is clear that;
∠CAE + ∠BAC + ∠BAD = 180° {beacuse of linear pair}
→ 108° + 3y + y = 180°
→ 4y = 180° - 108°
→ 4y = 72°
→ y = 72\°/4 = 18°
This means that ∠BAD = y = 18° and ∠BAC = 3y = 3 × 18 = 54°.
Now, as it is given that AB = DB, which means that ∠BDA = ∠BAD {because equal sides have equal opposite angles}
Now, in △BAD, applying angle sum property of the triangle we get;
∠BDA + ∠BAD + ∠ABD = 180°
18° + 18° + ∠ABD = 180°
∠ABD = 180° - 36° = 144°
Now, it is stated that the sum of interior angles is equal to the exterior angle, that means;
∠BAC + ∠BCA = ∠ABD
→ 54° + x = 144°
→ x = 144° - 54° = 90°
Hence, the value of x is 90°.
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