Math Is Fun Forum

eclipse4227

Member

Registered: 2007-04-23

Posts: 10

verifying identities

here it is:
secA+cscA-cosA-sinA=sinAtanA+cosAcotA

Last edited by eclipse4227 (2008-03-08 11:41:12)

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: verifying identities

LaTeX doesn't seem to be working, so I will have to try it without.

LHS = 1/cosA + 1/sinA - cosA/1 - sinA/1
     
      = (sinA + cosA - cos²AsinA - sin²AcosA) / (cosAsinA)
     
      = (sinA + cosA - (1-sin²A)sinA - (1-cos²A)cosA) / (cosAsinA)

      = (sinA + cosA - sinA + sin³A - cosA + cos³A) / (cosAsinA)

      = (sin³A+ cos³A) / (cosAsinA)

      = (sin³A /cosAsinA) + (cos³A/cosAsinA)

      = sinAtanA + cosAcotA

      = RHS

eclipse4227

Member

Registered: 2007-04-23

Posts: 10

Re: verifying identities

how did you get form the first line to the second line?

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: verifying identities

I combined the four fractions into one fraction using a denominator of cosAsinA

eclipse4227

Member

Registered: 2007-04-23

Posts: 10

Re: verifying identities

ok, thanks

Last edited by eclipse4227 (2008-03-08 11:39:38)