Помогите 1 - sin ^2 ( 3p/2 + a) / 1 - sin ^2 (p+a)

1-(sin3p/2×cosa+sinacis3p/2)^2
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1-(sinpcosa+sinacosp)^2


=(1-(-cosa)^2)/(1-(-sina)^2) =
(1-cos^2a)/(1-sin^2a)=
(cos^2a +sin^2a -cos^a)/(cos^2a+sin^2a-sin^2a)=sin^2a / cos^2a= tg^2a