1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple trigonometry question

  1. Oct 6, 2012 #1
    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?


    Attached Files:

  2. jcsd
  3. Oct 6, 2012 #2
    They don't give different values.
  4. Oct 6, 2012 #3
    My calculator gives 8cos70 = 5.067 and 8sin20 = 7.304.
  5. Oct 6, 2012 #4
    just realised it was in raidians mode. Whoops!
  6. Oct 6, 2012 #5


    User Avatar
    Homework Helper

    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:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook