## highschoolmom2010 Group Title trigonometric functions 11 months ago 11 months ago

1. highschoolmom2010 Group Title

2. agent0smith Group Title

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 Group Title

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

4. agent0smith Group Title

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 Group Title

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

6. pgpilot326 Group Title

tan 45 = 1. tan 22.5 <> .5

7. agent0smith Group Title

^that also disproves it, @highschoolmom2010

8. katherine.ok Group Title

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

9. terenzreignz Group Title

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

10. agent0smith Group Title

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 Group Title

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

12. terenzreignz Group Title

Noted :)

13. katherine.ok Group Title

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

14. agent0smith Group Title

@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 Group Title

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

16. katherine.ok Group Title

I think as simple as this sound...

17. katherine.ok Group Title

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 Group Title

^ good point.

19. highschoolmom2010 Group Title

im lost on all of this tbh....