Help with radians question please?

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The perimeter of a sector of a circle of radius rcm and angle x radians is the same as the perimeter of an equilateral triangle of side rcm. Show that x=1.

Can anyone help, I've sort of worked it out but I don't think I've done the correct wayto have gotten all the marks had it been in an exam, anyone know how to do it properly?

 

Posted Thu 4th April, 2013 @ 12:23 by Kate Westall

4 Answers

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This is AS AQA by the way

Answered Thu 4th April, 2013 @ 12:27 by Kate Westall
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Perimeter of sector       =        perimeter of equilateral triangle    (state that both sides equal)

r + r + (r*x)                =            r + r + r                                   (simplify)

2r + (r+x)                   =             3r                                           (minus 2r from both sides)

r*x                             =              r                                           (divide both sides by r)

  x                              =             r/r                                         (r divided by itself equals 1)

  x                              =              1                                         

Answered Sat 6th April, 2013 @ 14:40 by Alex
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I didnt format it very well so some of the explanation has moved onto the next line, sorry!

Answered Sat 6th April, 2013 @ 14:42 by Alex
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Thank you very much! I ended up finding the angles in triangle, but didn't know where to go! Haha. Thanks again :)

Answered Mon 8th April, 2013 @ 16:20 by Kate Westall