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If cos alpha + 2 cos beta +3 cos gamma ...

If `cos alpha + 2 cos beta +3 cos gamma = sin alpha + 2 sin beta + 3 sin gamma y = 0`, then the value of `sin 3alpha + 8 sin 3beta + 27 sin 3gamma ` is

A

`sin(a+ b+ gamma)`

B

`3 sin (alpha + beta + gamma)`

C

` 18 sin(alpha + beta + gamma)`

D

`sin(alpha+ beta + gamma)`

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The correct Answer is:
To solve the problem, we start with the given equation: \[ \cos \alpha + 2 \cos \beta + 3 \cos \gamma = \sin \alpha + 2 \sin \beta + 3 \sin \gamma = 0 \] ### Step 1: Represent the equations in complex form We can express the trigonometric functions in terms of complex exponentials. Let: - \( A = \cos \alpha + i \sin \alpha \) - \( B = \cos \beta + i \sin \beta \) - \( C = \cos \gamma + i \sin \gamma \) Thus, we can rewrite the equation as: \[ A + 2B + 3C = 0 \] ### Step 2: Separate real and imaginary parts From the equation \( A + 2B + 3C = 0 \), we can separate the real and imaginary parts: - Real part: \( \cos \alpha + 2 \cos \beta + 3 \cos \gamma = 0 \) - Imaginary part: \( \sin \alpha + 2 \sin \beta + 3 \sin \gamma = 0 \) ### Step 3: Apply the identity for cubes Using the identity for the sum of cubes, we know that: \[ x^3 + y^3 + z^3 = 3xyz \quad \text{if} \quad x + y + z = 0 \] Let: - \( x = A \) - \( y = 2B \) - \( z = 3C \) Then we can write: \[ A^3 + (2B)^3 + (3C)^3 = 3 \cdot A \cdot (2B) \cdot (3C) \] ### Step 4: Calculate the cubes Calculating the cubes gives us: \[ A^3 + 8B^3 + 27C^3 = 18ABC \] ### Step 5: Relate to sine functions From the earlier steps, we can relate the sine functions: \[ \sin 3\alpha + 8 \sin 3\beta + 27 \sin 3\gamma = 18 \sin(\alpha + \beta + \gamma) \] ### Step 6: Conclusion Since we have established that: \[ \sin 3\alpha + 8 \sin 3\beta + 27 \sin 3\gamma = 18 \sin(\alpha + \beta + \gamma) \] and given that \( \sin \alpha + 2 \sin \beta + 3 \sin \gamma = 0 \), we can conclude that: The value of \( \sin 3\alpha + 8 \sin 3\beta + 27 \sin 3\gamma \) is: \[ \boxed{0} \]

To solve the problem, we start with the given equation: \[ \cos \alpha + 2 \cos \beta + 3 \cos \gamma = \sin \alpha + 2 \sin \beta + 3 \sin \gamma = 0 \] ### Step 1: Represent the equations in complex form We can express the trigonometric functions in terms of complex exponentials. Let: ...
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