If tan theta = 5/12 then cos θ =
(A)12/13
(B)+ - 12/13
© 5/13
(D) ± 5/13
(E)12/11
I just found theta and replaced it in cos and the answer was A but the answer key said B.
Which one is correct?
@gameplayer1234 B, you don’t know whether cos θ (or sin θ) is positive or negative, all you know is their ratio is 5/12.
If you found cos (arctan (5/12)) on a calculator, this is not quite correct since arctan only returns an angle in the range (-pi/2, pi/2).
Oh okay so since tan equals 5/12, which is a positive value this means that both sin and cos can be postive (case1) or both negative(case2) to give a positive value of 5/12. That is why we chose ± 12/13 , which is taking both cases when sin is negative and postive. correct ? @MITer94
@gameplayer1234 Yep. Specifically, θ could be the angle such that sin θ = 5/13 and cos θ = 12/13, or sin θ = -5/13 and cos θ = -12/13.