Kindly explain those two steps

this is the property of trigonometric functions....

sin(π-2X) = sin2x, this is property. cos (π/4) = sin(π/4) = 1/√2. so apply sin(a+b) property here we put X= π/4 -t so angle in last term can make @=π/4+π/4-t. so sin@ changes in...