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In triangle ABC,AB=AC=x,∠ABC=θABC, AB = AC = x, ∠ABC = \theta and the circumradius is equal to yy. Then xy\frac{x}{y} equals

Solution

✅ Correct Option: 4

We have an isosceles triangle where AB=AC=xAB = AC = x, ∠ABC=θ\angle ABC = \theta, and circumradius =y= y.

Since AB=ACAB = AC, the base angles are equal:

∠ABC=∠ACB=θ\angle ABC = \angle ACB = \theta

So the third angle is:

∠BAC=180°−2θ\angle BAC = 180° - 2\theta


Using the Sine Rule, for any triangle with circumradius RR:

asin⁡A=2R\dfrac{a}{\sin A} = 2R

where aa is the side opposite to angle AA.


Picking side AB=xAB = x, the angle opposite to it is ∠ACB=θ\angle ACB = \theta.

Applying the Sine Rule:

xsin⁡θ=2y\dfrac{x}{\sin \theta} = 2y

x=2ysin⁡θx = 2y \sin \theta


xy=2sin⁡θ\dfrac{x}{y} = 2\sin\theta

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