Question

From the Cartesian coordinates (2,-10), I want (r, theta). So far, I have that r=sqrt(104). For the angle, I took the fact sqrt(104)*sin(theta)=2/sqrt(104). Now, sin(theta)=2/104, giving theta=asin(1/52). That *seems* right. "Ding! Survey *SAYS!* Nope." :/

Answer 1

well. your "r" is correct since \(\bf r=\sqrt{x^2+y^2}\)

now to find the angle
( 2 , -10 )
x y
thus \(\bf tan(\theta)=\cfrac{y}{x}\to \cfrac{-\cancel{ 10 }}{\cancel{ 2 }}\to -5\quad thus
\\ \quad \\
tan^{-1}[tan(\theta)]=tan^{-1}(-5)\implies \theta=tan^{-1}(-5)\)

Answer 2

Funny, that is *exactly* what I tried the first time. I should have mentioned, it's looking for answers with r>=0 and 0<theta<2pi.

Answer 3

I got the same answer, fwiw. :)

Answer 4

well... the "r" you found Is >=0 and the angle that gives will be within that range

Answer 5

I thought so, too.

Answer 6

I'm thinking is expecting a constant value

Answer 7

I'm not sure I follow.

Answer 8

is not expecting sqrt(...) operation or atan() operation
is expecting a solid number for both

Answer 9

Actually, it accepted atan(3/19) for the previous problem. Anyhow, I'll check in a little later...I've been neglecting the wife and kids for a big chunk of the day now. The little one is leaning on my leg, begging to go outside and play. Hard to say no to her. :)

Answer 10

hehe, indeed

Answer 11

I'm closing this one for now. Final is next week, and I'd rather not get stuck. There were already two problems on this assignment where I technically had the right answer, but the system wouldn't give me credit. Kind of annoying. :/ Thanks for your help!