How do you verify the identify $(1-sintheta)(1+sintheta)=cos^2theta$ ?

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Answer 1 · 2016-08-27T05:41:35

We will use the following well known identities:

With those, starting from the left hand side:

$(1-sin(theta))(1+sin(theta))$

$=1^2-sin^2(theta)$

$=(sin^2(theta)+cos^2(theta))-sin^2(theta)$

$=cos^2(theta)$

How do you verify the identify (1-sintheta)(1+sintheta)=cos^2theta(1-sintheta)(1+sintheta)=cos^2theta?