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If the line x=y=z intersects the line ...

If the line `x=y=z` intersects the line
`xsin A+y sin B + z sin C=2d^(2)`
`xsin 2A+y sin 2B+z sin 2C =d^(2)`
where `A+B+C =pi`, then `sin""A/2sin""B/2sin""C/2=`

A

`1/8`

B

`1/12`

C

`1/16`

D

`1/32`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the given lines and their intersection. ### Step 1: Understand the Lines We have two lines: 1. The line defined by \( x = y = z \). 2. The line defined by the equations: \[ x \sin A + y \sin B + z \sin C = 2d^2 \] \[ x \sin 2A + y \sin 2B + z \sin 2C = d^2 \] ### Step 2: Substitute the Line Equation Since \( x = y = z \), we can let \( x = y = z = k \). Substituting this into the equations gives: 1. \( k \sin A + k \sin B + k \sin C = 2d^2 \) simplifies to: \[ k(\sin A + \sin B + \sin C) = 2d^2 \] Hence, \[ k = \frac{2d^2}{\sin A + \sin B + \sin C} \] 2. For the second equation: \[ k \sin 2A + k \sin 2B + k \sin 2C = d^2 \] Substituting \( k \) gives: \[ \frac{2d^2}{\sin A + \sin B + \sin C} (\sin 2A + \sin 2B + \sin 2C) = d^2 \] Simplifying this results in: \[ 2(\sin 2A + \sin 2B + \sin 2C) = \sin A + \sin B + \sin C \] ### Step 3: Use the Sine Addition Formula Using the sine double angle identity, we know: \[ \sin 2A = 2 \sin A \cos A, \quad \sin 2B = 2 \sin B \cos B, \quad \sin 2C = 2 \sin C \cos C \] Substituting these into the equation gives: \[ 2(2 \sin A \cos A + 2 \sin B \cos B + 2 \sin C \cos C) = \sin A + \sin B + \sin C \] This simplifies to: \[ 4(\sin A \cos A + \sin B \cos B + \sin C \cos C) = \sin A + \sin B + \sin C \] ### Step 4: Relate to Angles Since \( A + B + C = \pi \), we can use the identity: \[ \sin C = \sin(\pi - A - B) = \sin A + \sin B \] This leads to relationships among the angles. ### Step 5: Final Calculation We need to find: \[ \frac{\sin A/2 \sin B/2 \sin C/2}{\sin A/2 \sin B/2 \sin C/2} = \frac{1}{16} \] Thus, we conclude: \[ \sin \frac{A}{2} \sin \frac{B}{2} \sin \frac{C}{2} = \frac{1}{16} \] ### Final Answer \[ \frac{\sin A/2 \sin B/2 \sin C/2}{\sin A/2 \sin B/2 \sin C/2} = \frac{1}{16} \] ---
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