1.

In `DeltaABC`, a =125, b=62 and c=123, find the value of sinB.

Answer» a=125, b=62, c=123
`therefore 2s=a+b+c`
`=125+62+123`
`=310`
`rArr s=155`
Now `sinB/2=sqrt((s-a)(s-c))/(ac)`
`=sqrt((155-125)(155-123))/(125 xx 123)`
`=sqrt(30 xx 32)/(123 xx 123)`
and `cosB/2=sqrt(s(s-b))/(ac)= sqrt(155 xx (155-62))/(125 xx 123)`
`=sqrt((155 xx 93)/(125 xx 123))`
and `cosB/2=sqrt((s(s-b))/(ac)) = sqrt((155 xx(155-62))/(125 xx 123)`
`=sqrt((155 xx 93))/(125 xx 123)`
`therefore sinB=2sinB/2 cosB/2`
`=2sqrt((30 xx 32)/(125 xx 123) xx (155 xx 93)/(125 xx 123))`
`(2 xx 3720)/(125 xx 23) = 496/1025`


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