A anna_sims New member Joined Oct 26, 2006 Messages 4 Oct 31, 2006 #1 I need some guidance on proving these identitles. Any help would be appreciated. 1) ((sec x+1)(sec x-1))/(2+(tan x+1)(tan x-1)) = sin^2 x 2) sec x + csc x = (1+tan x/sin x)
I need some guidance on proving these identitles. Any help would be appreciated. 1) ((sec x+1)(sec x-1))/(2+(tan x+1)(tan x-1)) = sin^2 x 2) sec x + csc x = (1+tan x/sin x)
A arthur ohlsten Full Member Joined Feb 20, 2005 Messages 847 Nov 1, 2006 #2 2) secx + cscx= [1+tanx]/sinx or 1/cosx + 1/sinx = [1+sinx/cosx] / sinx multiply both sides by sinx sinx/cosx +1 =1+ sinx/cosx proof 1) [secx+1][secx-1] --------------------- = sin^2x 2+[tanx+1][tanx-1] [ 1/cosx+1][1/cosx -1] ------------------------------------- = sin^2x 2+ [sinx/cosx +1][sinx/cosx -1] [ 1+cosx][1-cosx] / cos^2x ---------------------------------------- = sin^2x 2+[sinx+cosx][sinx-cosx]/cos^2x multiply numerator and denominator by cos^2x x not =90,270 degrees [1+cosx][1-cosx] ------------------------------------- = sin^2x 2cos^2x+[sinx+cosx][sinx-cosx] [1-cos^2x] ------------------------------------- = sin^2x 2 cos^2x+sin^2x-cos^2x sin^2x / [sin^2x+cos^2x] = sin^2x sin^2x=sin^2x proof Arthur
2) secx + cscx= [1+tanx]/sinx or 1/cosx + 1/sinx = [1+sinx/cosx] / sinx multiply both sides by sinx sinx/cosx +1 =1+ sinx/cosx proof 1) [secx+1][secx-1] --------------------- = sin^2x 2+[tanx+1][tanx-1] [ 1/cosx+1][1/cosx -1] ------------------------------------- = sin^2x 2+ [sinx/cosx +1][sinx/cosx -1] [ 1+cosx][1-cosx] / cos^2x ---------------------------------------- = sin^2x 2+[sinx+cosx][sinx-cosx]/cos^2x multiply numerator and denominator by cos^2x x not =90,270 degrees [1+cosx][1-cosx] ------------------------------------- = sin^2x 2cos^2x+[sinx+cosx][sinx-cosx] [1-cos^2x] ------------------------------------- = sin^2x 2 cos^2x+sin^2x-cos^2x sin^2x / [sin^2x+cos^2x] = sin^2x sin^2x=sin^2x proof Arthur