Trigonometric functions problem

  • Thread starter luludatis
  • Start date
  • #1
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Homework Statement


Find x

base of triangle: 2 pieces, 8+12
opposite end: x
angle: [tex]\Theta[/tex] ; angle formed by triangle of 8 units and x : 2[tex]\Theta[/tex]


Homework Equations


tan[tex]\Theta[/tex] = opp/adj
tan 2[tex]\Theta[/tex] = 2tan/1-tan2

The Attempt at a Solution


tan[tex]\Theta[/tex]= x/20
tan 2[tex]\Theta[/tex] = x/8

x/8=tan2[tex]\Theta[/tex]= 2(x/20) / 1-(x/20)2

(2x/20) / ((400-x2)/400) = 40x/400-x2

x/8=40x/400-x2

320x=400x-x3
x3-80=0


and now I'm stuck. I want to use difference of cubes, but i feel it is getting too complicated...
 

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Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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welcome to pf!

hi luludatis! welcome to pf! :smile:
320x=400x-x3
x3-80=0

oooh :cry:

you lost an x ! :blushing:
 
  • #3
6
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...i'm confused :P
 
  • #4
tiny-tim
Science Advisor
Homework Helper
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x3 - 80x = 0 :wink:
 
  • #5
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oooooooooooooooh!!!!! great! that fixes everything!! thank you!!
 

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