Question 287515
1/√(〖1 - ( x / ( y) )〗^2 )X (1/y)
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1/sqrt([1-(x/y)]^2  times (1/y)
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= 1/sqrt([(y-x)/y])^2 times (1/y)
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= 1/[(y-x)/y] [1/y]
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= y^2/(y-x)
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Cheers,
Stan H.