Prove that sin 3 is equal to 3 sin A minus 4 sin cube a
Proof:-
LHS=
=Sin3x
=sin(2x+x)
=sin2x.cosx+cos2x.sinx
=2sinx.cosx.cosx+cos^2x -sin^2).sinx
=2sinx.cos^2x+cos^2x.sinx-sin^3x
=2sinx(1-sin^2x) +(1-sin^2x). sinx-sin^3x
=2sinx-sin^3x+sinx-sin^3x-sin^3x
=3sinx - 4sin^3x proved..........
Formula sin3x in term of sinx see video lecture and if you learn then pls subscribe.
prove that cos3x=4cos^3x-3cosx
