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# polar coordinates watch

1. hello,

my book says that if i replace x=rcost and y=rsint in

f(x,y) = [(x+y)^2]/[(x^2)+(y^2)]

i should get

f = 2sin^2[t+(pi/4)]

however i get f= 1+sin2t,

where am i going wrong?

Tx
2. (Original post by pepsigirl)
hello,

my book says that if i replace x=rcost and y=rsint in

f(x,y) = [(x+y)^2]/[(x^2)+(y^2)]

i should get

f = 2sin^2[t+(pi/4)]

however i get f= 1+sin2t,

where am i going wrong?

Tx

Post ur working mate, we will have a look.
3. (Original post by wizz_kid)
Post ur working mate, we will have a look.
what do you mean,... that is my working???
4. (Original post by pepsigirl)
hello,

my book says that if i replace x=rcost and y=rsint in

f(x,y) = [(x+y)^2]/[(x^2)+(y^2)]

i should get

f = 2sin^2[t+(pi/4)]

however i get f= 1+sin2t,

where am i going wrong?

Tx

Bear with me, i'm posting the working.

Sub in the values, take r^2 out of the bracket and do some cancellations. You should get the answer. As i said before, post your solution, we'll see where u've gone wrong.
5. (Original post by wizz_kid)
... As i said before, post your solution, we'll see where
u've gone wrong.
actually it would help me personally if you were a bit less arrogant
6. (Original post by pepsigirl)
actually it would help me personally if you were a bit less arrogant
Mate, if i just give you the solution, would u remember how to do it in the exam? If you have attempted it, post ur working and we will check where u've gone wrong so that u wont make that mistake again (as u would know what to do).

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