Question

1- sin 2a= (sin a-cos a)^2

Answer 1

$1-sin(2a)=(sin a - cos a)^2$

1-sin(2a); sin(2a) = 2sin(a)cos(a)
1-2cos(a)sin(a); 1 = $sin^2a + cos^2a$
$cos^2 a -2cos(a)sin(a)+sin^2a$ 
$(sin(a) - cos(a) )^2$

$=\ \textgreater \ (sin(a) - cos(a))^2 = (sin(a)-cos(a))^2 -Adevarat$