musicdramalife00 Group Title write each polar equation in rectangular form: r=-3sec(Theta) r=costheta+sintheta r=5/3costheta+8sin 8 months ago 8 months ago

1. musicdramalife00 Group Title

^theta after the last sin

2. myininaya Group Title

You need to use these equations: $r^2=x^2+y^2 ; rcos(\theta)=x ; rsin(\theta)=y$

3. musicdramalife00 Group Title

i did, but like it ended up like x^2+y^2= 25+9x^2r^2-30xr/64y^2 for the last one

4. myininaya Group Title

We want the equations just in terms of x and y instead of r and theta.

5. musicdramalife00 Group Title

i don't know what i did wrong

6. myininaya Group Title

so the last one is: $r=\frac{5}{3}\cos(\theta)+8\sin(\theta)$?

7. musicdramalife00 Group Title

no uh (5)/(3costheta+8sintheta)

8. myininaya Group Title

oh so you meant 5/(3costheta)+8sin(theta)) and not 5/3cos(theta)+8sin(theta)

9. musicdramalife00 Group Title

mhm 5 / (3cos+8sin)

10. myininaya Group Title

$r= \frac{5}{3\cos(\theta)+8\sin(\theta)}$ Multiply both sides by that one fraction's denominator

11. myininaya Group Title

$r(3\cos(\theta)+8\sin(\theta))=5$ Distribute then substitute the equations I gave you

12. musicdramalife00 Group Title

3xr+8ry=5 but then you'll need to put r on one side cause you would need to square it. and the answer comes out all weird

13. myininaya Group Title

well rcos(theta) is x not just cos(theta same thing with the y deal rsin(theta) is y not just sin(theta)

14. musicdramalife00 Group Title

whoops how about the secant one

15. myininaya Group Title

put it in terms of cos by using an identity

16. myininaya Group Title

then put it in some form where you can use the equations I gave you

17. musicdramalife00 Group Title

sosoososososo it would be x^3+y^2x=-3 AND uh the other one x^2+y^2=x+y?

18. myininaya Group Title

for the first one? no...

19. myininaya Group Title

I haven't looked at the second one... You are making this way too hard it looks like.

20. myininaya Group Title

first one you did this as first step right?: $r=\frac{-3}{\cos(\theta)}$

21. musicdramalife00 Group Title

yep

22. myininaya Group Title

Notice this only has a cos in it... how do you get cos with the r over there so you can use the equation rcos(theta)=x

23. musicdramalife00 Group Title

multiply both sides with r

24. myininaya Group Title

no

25. myininaya Group Title

try again

26. myininaya Group Title

How do you undo multiplication?

27. myininaya Group Title

Or division?

28. musicdramalife00 Group Title

oh omg

29. myininaya Group Title

we have division by cos to undo that you ?

30. musicdramalife00 Group Title

x=-3

31. myininaya Group Title

yes

32. musicdramalife00 Group Title

thanks

33. myininaya Group Title

so for that second one...

34. myininaya Group Title

you actually got it right

35. myininaya Group Title

but how did you go about it you didn't choose a complicated way right?

36. musicdramalife00 Group Title

yep uh multiplied both side with r and then substituted the stuff in

37. myininaya Group Title

oh good

38. myininaya Group Title

do you have any other questions? do you think you got this better?

39. musicdramalife00 Group Title

uh yea i have a few more

40. musicdramalife00 Group Title

for standard forms of polar equation uh how would graph r=2cos3theta

41. myininaya Group Title

Plug in values of theta and see what the r output is

42. myininaya Group Title

then remember how you graph using polar coordinates r is the distance from the origin and direction is given by r to from the angle theta is the angle

43. musicdramalife00 Group Title

like how would you do this with a graphing calculator

44. myininaya Group Title

So for example if I plug in theta=0 $r=2 \cos (3 \cdot 0)=2\cos(0)=2(1)=2 => \text{ graph the point } (2,0^o)$ |dw:1388269865874:dw|

45. myininaya Group Title

find 0 degrees and then go to the circle with radius 2

46. musicdramalife00 Group Title

cause wksht says not to use a table

47. myininaya Group Title

|dw:1388269927627:dw| then plug in more points

48. musicdramalife00 Group Title

oh i know how to graph but not without plugging in points

49. myininaya Group Title

I haven't looked at a calculator in ages

50. myininaya Group Title

did you try looking up how to input polar equations into whatever calculator type you have

51. myininaya Group Title

some calculators require a difference procedure in order to do certain things

52. myininaya Group Title
53. myininaya Group Title

find mode and choose polar or pol or polargc

54. myininaya Group Title

then just type your equation in

55. musicdramalife00 Group Title

u what's the website

56. musicdramalife00 Group Title

*uh

57. myininaya Group Title

What ?