Question 983552
if sin 21 degree = x/y, then sec 21 degree - sin 69 degree is equal to ? 
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{{{cos(21) = sqrt(1 - sin^2(21)) = sqrt((y^2-x^2)/y^2) = sqrt(y^2-x^2)/y}}}
sec = 1/cos
sin(69) = cos(21)
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sec 21 degree - sin 69 degree
= 1/cos(21) - cos(21)
= (1 - cos^2(21))/cos(21)
= sin^2(21)/cos(21)
= {{{(x^2/y^2)/(sqrt(y^2-x^2)/y)}}}
= {{{x^2/(y*sqrt(y^2-x^2))}}}
= {{{x^2*sqrt(y^2-x^2)/(y*(y^2-x^2))}}}