## kaylala one year ago Trigonometric Equation 2tan^2A + 3secA = 0

1. kaylala

2. hartnn

which pythagorean identities do you know ?

3. kaylala

I've bee through all except for the half identities

4. kaylala

@hartnn

5. hartnn

so which identity relates tan^2 A and sec^2 A ?

6. kaylala

Sin?

7. kaylala

I mean cos?

8. hartnn

ever sen this ? \(\\tan^2 A =sec^2A-1\) ? use it here

9. kaylala

Yes. I'm familiar with that Wait. Let me try

10. kaylala

I got 2x^2+3x-2 Is it right? So i may move on

11. hartnn

yes, that = 0 remember its an equation, not an expression

12. kaylala

Oh right

13. kaylala

How'll this be nothing will equal to 3x?

14. kaylala

@hartnn ^

15. hartnn

what ? i didn't get your question...

16. hartnn

2x^2+3x-2 = 0 x= ..... x=....

17. kaylala

Oh sorry What i meant was what should i do next? How do i find x? I cant use the FOIL method.

18. hartnn

factor method. 2 numbers with sum = +3 and product = -4

19. kaylala

Got it Wait

20. kaylala

Sec = 1/2 Sec={no solution Sec=-2 No solution ????? I dont know Hpw's this? @hartnn

21. hartnn

sec A can be -2

22. kaylala

I dont see any negative 2 in the graph list Sec A =-2

23. hartnn

sec A = -2 secA = 1/cos A cos A = -1/2 when ?

24. kaylala

I dont see any cos A =-1/2 There is only cos A=1/2

25. kaylala

Or did i get it wrong?

26. kaylala

@hartnn ^

27. hartnn

how about angles 120 and 210 ?

28. kaylala

Where did you get that. Those arent in the graph that was given to us

29. hartnn
30. kaylala

Oh i see now So will the answer for secA=-2 or cosA=-1/2 be: A={120,210}

31. kaylala

Is that it already? How about sec=1/2? Does it really have no solution? @hartnn

32. hartnn

yes. in the range 0 to 360. range of sec function does not include values between -1 and 1 so, sec A = 1/2 will have no solution, (in the same way cos A = 2 have no solution)

33. kaylala

Okay thanks again

34. hartnn

welcome ^_^