please answer this question

Active member

u can answer it at yahoo answer as well click here

affraid

register at icse.forumotion.com if you liked the question to get more such cool questions from its members. Very Happy

Active member

question was
Trigonometry:given that : sin a + cos a=1 hence prove that sin a - cos a= +1 & also sin a - cos a=-1.

answer
sina+cosa=1 --->square both sides
sin^a+cos^2a +2sin cosa =1
1 + 2sina cosa =1
2sina cosa =0
so
(sina -cosa)^2 = sin^2 a +cos^2 a -2sina cosa =1 - 0 = 1

so
(sina - cosa)^2 =1
sina -cosa = +/-1
so
either
sina - cosa =1
or sina -cosa = -1

answered by mbdwy