Question

if cosA-SinA =1 then prove that cosA+sinA=±1

Answer 1

on squaring both side
sin2+cos2-2sincos =1
-2sincos =1-1
sincos =-0
2sincos = 0
on adding 1 both sides
sin2 +cos2+2sincos =1
(sin+cos)^2=1
sin +cos =root 1 =+-1

Answer 2

Refer the attachment for the solution.

Thanks