√sin A − √sin B√sin A + √sin B=a+b−2√aba−b
√sin A−√sin B√sin A+√sin B=a+b−2√aba−bRHSa+b−2√aba−b=(√a)2+(√b)2−2√ab(√a)2−(√b)2=(√a−√b)2(√a)2−(√b)2=(√a−√b)(√a+√b)=(√k sin A−√k sin B)(√k sin A+√k sin B)=(√sin A−√sin B)(√sin A+√sin B)[taking k common and cancelling them]=LHSHence proved.