## highschoolmom2010 one year ago trigonometric functions

1. highschoolmom2010

2. agent0smith

Well, you can start by testing a couple of values, to disprove it immediately try A=30 and B=59 Tan30 + tan59 = tan89 ?

3. terenzreignz

I for one, do not recall the tangent identity to be quite as simple as tan(A) + tan(B) = tan(A + B)...

4. agent0smith

It's not @terenzreignz, but the question states for A+B< 90 which makes it not able to be an identity. But it's easy to disprove.

5. terenzreignz

Why not tan(45) + tan(30) = tan(75) :)

6. pgpilot326

tan 45 = 1. tan 22.5 <> .5

7. agent0smith

^that also disproves it, @highschoolmom2010

8. katherine.ok

basically tana+tanb= (sinacosb+sinbcosa)/cosacosb= sin(a+b)/cosacosb

9. terenzreignz

At least we have exact values for these stuff :3 $\Large \tan(45^o) = 1\\\Large \tan(30^o)=\frac1{\sqrt{3}}$

10. agent0smith

My reasoning for picking a A+B close to 90, was due to tan90 being undefined, so it's highly unlikely two smaller angles will give anything close to the tangent of an angle near 90

11. katherine.ok

=(sinacosb+cosasinb)/cosacosb=/= sinasinb/cosacosb

12. terenzreignz

Noted :)

13. katherine.ok

Now i need to somehow prove sinacosb+sinbcosa=/=sinasinb...

14. agent0smith

@katherine.ok based on her other questions, I don't think she's at the level of trigonometry where they're using proofs. I think it's more an analytical question.

15. pgpilot326

tan 60 + tan (-30) <> tan 30

16. katherine.ok

I think as simple as this sound...

17. katherine.ok

by using the tangent graph, adding a random point where x is (0,90),you will not get tan a+ tan b because it is not linear graph.

18. agent0smith

^ good point.

19. highschoolmom2010

im lost on all of this tbh....