1.

If cos `(alpha+beta)=0`, then `sin(alpha-beta)`canbe reduced to : (a) `cosbeta` (b)`cos2beta` ( c) `sinalpha` (d) `sin2alpha`

Answer» Given that , `cos(alpha+beta)=0=cos90^(@)`
`:. alpha+beta=90^(@)`
`:.alpha=90^(@)-beta`
`:.sin (alpha-beta)=sin[(90^(@)-beta)]=sin(90^(@)-2beta)=cos2beta`


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