How do you evaluate $cos[2arcsin(7/25)]$ ?

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Answer 1 · 2018-08-09T15:31:36

$527/625 = (17*31)/5^4$

if $sin alpha = 7/25$ then how much is $x = cos 2alpha$ ?

$x = cos^2 alpha - sin^2 alpha = 1 - 2 sin^2 alpha = 1 - (2*49)/625$

$x = (625 - 98)/625$

How do you evaluate cos[2arcsin(7/25)]cos[2arcsin(7/25)]?