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In a Delta ABC, 2 sinA cos B + 2 sin B c...

In a `Delta ABC`, 2 sinA cos B + 2 sin B cos C + 2 sin cos A = sin A + sin B + sin C, then `Delta ABC`is

A

isosceles

B

right angled

C

acute angled

D

none of these

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To solve the problem, we need to analyze the equation given in the triangle ABC: \[ 2 \sin A \cos B + 2 \sin B \cos C + 2 \sin C \cos A = \sin A + \sin B + \sin C \] ### Step 1: Rewrite the left-hand side using the sine addition formula We can use the sine addition formula, which states that \(2 \sin x \cos y = \sin(x+y) + \sin(x-y)\). Applying this to each term: 1. \(2 \sin A \cos B = \sin(A + B) + \sin(A - B)\) 2. \(2 \sin B \cos C = \sin(B + C) + \sin(B - C)\) 3. \(2 \sin C \cos A = \sin(C + A) + \sin(C - A)\) Thus, we can rewrite the left-hand side as: \[ \sin(A + B) + \sin(A - B) + \sin(B + C) + \sin(B - C) + \sin(C + A) + \sin(C - A) \] ### Step 2: Substitute \(A + B + C = 180^\circ\) Since in triangle ABC, \(A + B + C = 180^\circ\), we can express \(A + B\), \(B + C\), and \(C + A\) in terms of \(C\), \(A\), and \(B\) respectively: - \(A + B = 180^\circ - C\) which gives \(\sin(A + B) = \sin C\) - \(B + C = 180^\circ - A\) which gives \(\sin(B + C) = \sin A\) - \(C + A = 180^\circ - B\) which gives \(\sin(C + A) = \sin B\) Thus, we can simplify the left-hand side to: \[ \sin C + \sin A + \sin B + \sin(A - B) + \sin(B - C) + \sin(C - A) \] ### Step 3: Set the equation Now, we can set the equation: \[ \sin C + \sin A + \sin B + \sin(A - B) + \sin(B - C) + \sin(C - A) = \sin A + \sin B + \sin C \] ### Step 4: Simplify the equation Subtract \(\sin A + \sin B + \sin C\) from both sides: \[ \sin(A - B) + \sin(B - C) + \sin(C - A) = 0 \] ### Step 5: Analyze the sine terms The equation \(\sin(A - B) + \sin(B - C) + \sin(C - A) = 0\) implies that the angles \(A\), \(B\), and \(C\) are such that: 1. \(A - B = 0\) or \(B - C = 0\) or \(C - A = 0\) 2. This means \(A = B\), \(B = C\), or \(C = A\). ### Conclusion Since we have established that two angles are equal, triangle ABC must be an **isosceles triangle**.

To solve the problem, we need to analyze the equation given in the triangle ABC: \[ 2 \sin A \cos B + 2 \sin B \cos C + 2 \sin C \cos A = \sin A + \sin B + \sin C \] ### Step 1: Rewrite the left-hand side using the sine addition formula We can use the sine addition formula, which states that \(2 \sin x \cos y = \sin(x+y) + \sin(x-y)\). Applying this to each term: ...
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