Answer:
:)
Step-by-step explanation:
For simplicity I will substitue [tex]x[/tex] for β.
[tex]1-sin(2x)=(cosx-sinx)^2\\1-2sin(x)cos(x)=cos^2x-2sin(x)cos(x)+sin^2x\\1=cos^2(x)+sin^2(x)\\1=1[/tex]
In the first step I used the identity
[tex]sin(2x)=2sin(x)cos(x)[/tex]
And I factored out [tex](cosx-sinx)^2[/tex]
Then it's just simple algebra to cancel till the 3rd step where we used another identity derived from the Pythagorean Theorem.
[tex]cos^2(x)+sin^2(x)=1[/tex]
That's it!
