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If cos^{-1}(x/a) + cos^{-1}(y/b) = alpha,

**Prove that, x**^{2}/a^{2} + y^{2}/b^{2} - 2xy/ab * [cos(alpha)]= sin^{2}(alpha)^{}

^{2}/a

^{2}+ y

^{2}/b

^{2}- 2xy/ab * [cos(alpha)]= sin

^{2}(alpha)

^{}