My Math Forum Trigonometric identity

 Algebra Pre-Algebra and Basic Algebra Math Forum

 May 3rd, 2009, 06:20 PM #1 Newbie   Joined: May 2009 Posts: 1 Thanks: 0 Trigonometric identity i need help with this, can anyone help please, tan? = 1 - cos2?/sin2? . \i've been stuck on this for a while, and i cannot figure it out, could someone show me how it is done. Thanks
May 4th, 2009, 04:48 PM   #2
Global Moderator

Joined: May 2007

Posts: 6,684
Thanks: 658

Re: Trigonometric identity

Quote:
 Originally Posted by munkiemunkie007 i need help with this, can anyone help please, tan? = 1 - cos2?/sin2? . \i've been stuck on this for a while, and i cannot figure it out, could someone show me how it is done. Thanks
Are you trying to solve an equation or prove an identity? It looks to me that it is not an identity.

May 4th, 2009, 05:50 PM   #3
Global Moderator

Joined: Dec 2006

Posts: 20,288
Thanks: 1968

Quote:
 Originally Posted by munkiemunkie007 tan? = 1 - cos2?/sin2?
I think you meant tan? = (1 - cos2?)/sin2? (provided sin(2?) is not zero).
Standard identities tell you that cos(2?) = 1 - 2 sin²? and sin(2?) = 2 sin(?)cos(?).
Hence (1 - cos(2?))/sin(2?) = 2 sin²? / (2 sin(?)cos(?)) = sin(?)/cos(?) = tan(?).

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post matemagia Trigonometry 4 August 30th, 2012 07:40 PM OriaG Trigonometry 10 August 12th, 2012 05:37 PM afrim Trigonometry 8 October 1st, 2011 02:59 AM chnixi Algebra 1 August 19th, 2009 04:52 AM TG Algebra 2 March 7th, 2008 04:22 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top