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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: 6,626 Thanks: 622  Re: Trigonometric identity Quote:
 
May 4th, 2009, 05:50 PM  #3  
Global Moderator Joined: Dec 2006 Posts: 19,865 Thanks: 1833  Quote:
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(?).  

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identity, trigonometric 
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