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AP EAMCET201825 Apr 2018Morning ShiftMathematicsProperties of TrianglesActual

In Δ A B C , a 3 cos B - C + b 3 cos C - A + c 3 cos A - B =

Options

  1. Aa b c
  2. Ba + b + c
  3. C2   a b c
  4. D3   a b c

Correct answer

D. 3   a b c

Step-by-step solution

We know that, sin 2 x + sin 2 y = 2 sin x + y cos x - y ⇒ cos x - y = sin 2 x + sin 2 y 2 sin x + y ⇒ cos x - y = 2 sin x cos x + 2 sin y cos y 2 sin x + y ⇒ cos x - y = sin x cos x + sin y cos y sin x + y Now, a 3 cos B - C = a 3 sin B cos B + sin C cos C sin B + C ⇒ a 3 cos B - C = a 3 sin B cos B + sin C cos C sin π - A ⇒ a 3 cos B - C = a 3 sin B cos B + sin C cos C sinA Now a 3 cos B - C = a 3 b k cos B + c k cos C a k a 3 cos B - C = a 2 b cos B + c cos C     . . .

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