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 Trigonometry Trigonometry Math Forum

 October 14th, 2010, 07:01 PM #1 Member   Joined: Sep 2010 Posts: 55 Thanks: 0 Sine If sin(x-pi)=A sin x, then the number A=___ I don't even know where to start. Please help. October 14th, 2010, 07:55 PM #2 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs Re: Sine sin(x - ?) = A sin(x) Use the additive angle identity for sine: sin(a � b) = sin(a)cos(b) � cos(a)sin(b). sin(x)cos(?) - cos(x)sin(?) cos(?) = -1, sin(?) = 0, thus -sin(x) = A sin(x) 0 = (sin(x))(A + 1) For sin(x) ? 0, A = -1 October 15th, 2010, 06:43 PM #3 Global Moderator   Joined: Dec 2006 Posts: 21,034 Thanks: 2271 Re: Sine Learn the identities below. sin(A) ? -sin(-A), � � �cos(A) ? cos(-A), � � � tan(A) ? -tan(-A) � � (if defined) sin(A) ? sin(? - A), � �cos(A) ? -cos(? - A), �tan(A) ? -tan(? - A) (if defined) sin(A) ? sin(A + 2?), cos(A) ? cos(A + 2?), tan(A) ? tan(A + ?) �(if defined) They imply that sin(x - ?) ? -sin(? - x) ? -sin(x) ? (-1)sin(x). Tags sine Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post alexmath Trigonometry 2 November 19th, 2012 02:20 AM johnny Calculus 1 March 12th, 2011 02:29 AM moja_a Trigonometry 8 February 27th, 2011 09:33 PM courteous Trigonometry 4 June 17th, 2010 05:51 AM jordanshaw Calculus 1 December 31st, 1969 04:00 PM

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