Homework Help: Trig Identities

ok ... heres my problem
i need to prove that the LHS = RHS


sin^2 + 2cos - 1 / 2 + cos - cos^2 = 1 / 1 + sec

i tried to use the pythagarean identies and substitute the 1 and 2
but tht isnt getting me anywhere .. plz help

 

ummm ok .. here's what i got


sin^2 + 2cos - 1 / 2 + cos - cos^2 = 1 / 1 + sec

LHS :

= sin^2 + cos + cos - sin^2 - cos^2 / 1 + sin^2 + cos^2 + cos - cos^2
... here i cancelled the "sin^2" and " - sin^2" on the top and in the bottom i cancelled the "cos^2" and " - cos^2"

= cos + cos - (cos)(cos) / 1 + sin^2 + cos

= cos + cos - cos^2 / sin^2 + cos^2 + sin^2 + cos

= cos + cos / sin^2 + sin^2 + cos

...... I dont noe what to do from here ... am i even tackling this problem the right way ??

RHS :

1 / 1 + sec

= 1 / 1 + 1/cos
= 1 + cos .... no problems here .. jus the LHS

 

there all sin(x) or cos(x) :tongue2:

 

itz

[tex]\frac{1}{1+\sec x}[/tex]