My Math Forum trick question

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 February 24th, 2013, 07:37 PM #1 Senior Member   Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0 trick question _____ -8sin^2(x) = 8cos^2(x)
 February 24th, 2013, 07:40 PM #2 Senior Member     Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 520 Math Focus: Calculus/ODEs Re: trick question Hint: $1-\sin^2(x)=\cos^2(x)$ Now multiply through by 8.
February 24th, 2013, 08:04 PM   #3
Math Team

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From: Lexington, MA

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Re: trick question

Hello, mathkid!

A strange way to write the problem . . .

Quote:
 $\text{Fill in the blank: }\;\_\!\_\!\_\!\_\,-\,8\sin^2x \:=\:8\cos^2x$

$\text{W\!e have: }\:Z \,-\,8\sin^2x \:=\:8\cos^2x$

[color=beige]. . . . . . . . . . . . . . . [/color]$Z \:=\:8\sin^2x\,+\,8\cos^2x$

[color=beige]. . . . . . . . . . . . . . . [/color]$Z \:=\:8\,\underbrace{(\sin^2x\,+\,\cos^2x)}_{\text{ This is 1}}$

[color=beige]. . . . . . . . . . . . . . . [/color]$Z \:=\:8$

 February 25th, 2013, 03:51 AM #4 Senior Member   Joined: Aug 2012 From: South Carolina Posts: 866 Thanks: 0 Re: trick question ok yes I know the sin squared + cos squared = 1 solving algebraically for the missing variable or blank was so simple seeing it now. I just need to practice the trig more. makes me want to puke sometimes...lol

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