# Math Help - Circle Angle, Time: xy coordinates

1. ## Circle Angle, Time: xy coordinates

A ferris wheel is rotating at the constant angular speed of 3 RPM counterclockwise. The platform of this ferris wheel is a circular disc of radius 24 feet. You jump onto the ferris wheel at the location pictured below.

If θ = 34o, then what are your xy coordinates after 4 minutes?
If θ = 20o, then what are your xy coordinates after 45 minutes?

So for both of these, which are similar problems, but different degree and timing, I'll start with the first one
First I know that the time is 4 minutes
I also know sin (34o) = 0.559192904
Then θ = wt = (3 rev/min)(4 minutes)(2pi/1rev) = 75.39822369 radians

Though, I'm not sure if I'm doing it right, since I kind of got lost, but I know the radius is 24
Then after I get the right degrees, then I would use rcosθ to find x, and rsinθ to find y

Can anyone help me out here? Thanks

2. ## Re: Circle Angle, Time: xy coordinates

Since you're travelling around the circle at 3 RPM, then after a full minute you have gone around 3 times, but are now back at your starting location. This is true for any number of minutes. So after 4 minutes you are again at your starting location and the same with 45 minutes. At that point you just calculate x and y as you've stated.

3. ## Re: Circle Angle, Time: xy coordinates

I did?
For the first one, the answer is: (-5.92564, 21.14892)
And the second one is: (19.07064, -10.89497)

I'm getting different numbers.

4. ## Re: Circle Angle, Time: xy coordinates

I just used $(24 cos 34 \degree , 24 sin 34 \degree ) \approx (19.9, 13.4)$ and similar for the next

5. ## Re: Circle Angle, Time: xy coordinates

Originally Posted by cshanholtzer
I just used $(24 cos 34 \degree , 24 sin 34 \degree ) \approx (19.9, 13.4)$ and similar for the next
The x seems similar, but the y are kind of completely different, one is negative and is 10, the other is positive and is 13

6. ## Re: Circle Angle, Time: xy coordinates

For the values of $\theta$ given you are in the first quadrant so should expect a positive value for both x and y.

7. ## Re: Circle Angle, Time: xy coordinates

Originally Posted by cshanholtzer
For the values of $\theta$ given you are in the first quadrant so should expect a positive value for both x and y.
Oh wow, I feel stupid. I posted the wrong answers, anyway I made it hard on myself.
It was just basically 24cos(34) and 24sin(34)...
And for the 2nd one is 24(cos20) and 24sin(20)