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If s inalpha+s inbeta=a\ a n d\ cosalpha...

If `s inalpha+s inbeta=a\ a n d\ cosalpha-cosbeta=b ,` then `tan(alpha-beta)/2=` `-a/b` b. ` b/a` c. `sqrt(a^2+b^2)` d. none of these

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`sin alpha +sin beta=a`
`2sin(frac{alpha+beta}{2})cos(frac{alpha-beta}{2})=a`
`-2sin(frac{alpha+beta}{2})sin(frac{alpha-beta}{2})=b`
`frac{-2sin(frac{alpha+beta}{2})sin(frac{alpha-beta}{2})}{2sin(frac{alpha+beta}{2})cos(frac{alpha-beta}{2})}=frac{b}{a}`
`-tan(frac{alpha-beta}{2})=frac{b}{a}`
`tan(frac{alpha-beta}{2})=-frac{b}{a}`
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