1. A
   $\frac{\pi}{2}$
2. B
   $\frac{\pi}{3}$
3. C
   $\cos^{-1}\left(\frac{3}{4}\right)$
4. D
   $\cos^{-1}\left(\frac{9}{14}\right)$

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1. A
   $\frac{1}{2},-2$
2. B
   $-\frac{1}{2},2$
3. C
   $-\frac{1}{2},-2$
4. D
   $\frac{1}{2},2$

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1. A
   $x+y+z=1$
2. B
   $x+y+z=2$
3. C
   $x+y+z=3$
4. D
   $x+y+z=4$

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1. A
   $0^\circ$
2. B
   $30^\circ$
3. C
   $45^\circ$
4. D
   $90^\circ$

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1. A
   $\frac{2}{3},\frac{-1}{3},\frac{2}{3}$
2. B
   $\frac{-2}{3},\frac{1}{3},\frac{-2}{3}$
3. C
   $\frac{2}{3},\frac{1}{3},\frac{2}{3}$
4. D
   $\frac{2}{3},\frac{-1}{3},\frac{-2}{3}$

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1. A
   $3x+2z-1=0$
2. B
   $3x-2z=1$
3. C
   $3x+2z+1=0$
4. D
   $3x+2z=2$

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1. A
   $17x-47y-24z+172=0$
2. B
   $17x+47y-24z+172=0$
3. C
   $17x+47y+24z+172=0$
4. D
   $17x-47y+24z+172=0$

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1. A
   $5$
2. B
   $3$
3. C
   $2$
4. D
   $-5$

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1. A
   $4x+y+5z=14$
2. B
   $4x-2y-5z=45$
3. C
   $x-2y-5z=10$
4. D
   $4x+y+6z=11$

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