One side of a triangle and a rectangle is the same. The third vertex of the triangle lies on the midpoint of the rectangle side opposite the common side. The rectangle sides are in the ratio 2 : 3 and the common side is the longer side of the rectangle.  What is the sin value of the angle between the common side and the equal side of the triangle?

One side of a triangle and a rectangle is the same. The third vertex of the triangle lies on the midpoint of the rectangle side opposite the common side. The rectangle sides are in the ratio 2 : 3 and the common side is the longer side of the rectangle.  What is the sin value of the angle between the common side and the equal side of the triangle? Correct Answer 4/5

Calculation:

Let 2a and 3a are sides of the rectangle, the triangle and rectangle will be as shown in the figure,

[ alt="F1 ravisharma Nishad 21.04.21 D5" src="//storage.googleapis.com/tb-img/production/21/04/F1_ravisharma_Nishad_21.04.21_D5.png" style="width: 141px; height: 133px;">

The three angles are ∠ AEC, ∠ EAC and ∠ ECA.

∠ EAC = ∠ECA  (∵  Δ AEC is an isosceles triangle with AE = EC)

Sin (∠ EAC) = 2a/EA

EA= (2a)2 + (1.5a)2 = 6.25a2

⇒ EA = 2.5a

∴ Sin (∠ EAC) = 2a/2.5a = 4/5

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