How do you simplify Sinx/(1-secx) - sin/(1+secx)sinx1secxsin1+secx?

1 Answer
Apr 19, 2016

We must remember that sec = 1/cossec=1cos

Explanation:

sinx/(1 - 1/cosx) - sinx/(1 + 1/cosx)sinx11cosxsinx1+1cosx

sinx/((cosx - 1)/cosx) - sinx/((cosx + 1)/cosx)sinxcosx1cosxsinxcosx+1cosx

sinx xx cosx/(cosx - 1) - sinx xx cosx/(cosx + 1)sinx×cosxcosx1sinx×cosxcosx+1

(sinxcosx)/(cosx - 1) - (sinxcosx)/(cosx + 1)sinxcosxcosx1sinxcosxcosx+1

((sinxcosx)(cosx + 1))/((cosx - 1)(cosx + 1)) - ((sinxcosx)(cosx- 1))/((cosx + 1)(cosx - 1))(sinxcosx)(cosx+1)(cosx1)(cosx+1)(sinxcosx)(cosx1)(cosx+1)(cosx1)

(sinxcos^2x + sinxcosx)/(cos^2x - 1) - (sinxcos^2x - sinxcosx)/(cos^2x - 1)sinxcos2x+sinxcosxcos2x1sinxcos2xsinxcosxcos2x1

(sinxcos^2x + sinxcosx - sinxcos^2x + sinxcosx)/(cos^2x - 1)sinxcos2x+sinxcosxsinxcos2x+sinxcosxcos2x1

(2sinxcosx)/(cos^2x - 1)2sinxcosxcos2x1

Applying the double angle identity 2sinxcosx = sin2x2sinxcosx=sin2x and the pythagorean identity cos^2x - 1 = -sin^2xcos2x1=sin2x we get the following:

(sin2x)/(-sin^2x) ->sin2xsin2x this is your answer.

*Beware: This is not the only possible answer; there are many ways of attacking this problem, with different answers completely within the realm of possibility. *

Hopefully this helps!