Simple trigonometry question

  • Thread starter smulc
  • Start date
  • #1
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I need to find the length AD. I thought that with the numbers given, and angle A worked out to being 70o there would be two different ways of working length AD out. I thought 8sin20 and 8cos70 would both be acceptable ways of calculating the length but they give different values. Where have I gone wrong?

Thanks.
 

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  • #2
296
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They don't give different values.
 
  • #3
33
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My calculator gives 8cos70 = 5.067 and 8sin20 = 7.304.
 
  • #4
33
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just realised it was in raidians mode. Whoops!
 
  • #5
Mentallic
Homework Helper
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94
My calculator gives 8cos70 = 5.067 and 8sin20 = 7.304.
and you should realize (hopefully quickly) that if cos60o=1/2 then cos70o must be less than half, so there is no way 8cos70o > 5, and similarly with sin20o :wink:
 

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