Parametric equations including addition

50 Views Asked by At

So I am familiar with finding the parametric equation given multiplicative $x$ and $y$ values but in a problem such as

$x=2+\cos(t)$,

$y=3+\sin(t)$,

$0\le t \le \frac{5\pi}{2}$

I cannot even make of what I am supposed to do to find what type of graph this will be on nor its direction.

1

There are 1 best solutions below

0
On BEST ANSWER

community wiki post so that the question can be closed

To expand on what was said in the comments, we have \begin{align*} x & = 2 + \cos t\\ y & = 3 + \sin t\\ \end{align*} where $0 \leq t \leq \frac{5\pi}{2}$.

We eliminate $t$. \begin{align*} x - 2 & = \cos t\\ y - 3 & = \sin t \end{align*} Squaring each equation and adding yields $$(x - 2)^2 + (y - 3)^2 = \cos^2t + \sin^2t$$ Using the Pythagorean Identity $\cos^2t + \sin^2t = 1$ yields $$(x - 2)^2 + (y - 3)^2 = 1$$ which is the equation of a circle with radius $1$ and center $(2, 3)$. For the entire circle to be traversed, the interval in $t$ must have length at least $2\pi$. Since $\frac{5\pi}{2} > 2\pi$, the entire circle is traversed. In fact, it is traversed $$\frac{\frac{5\pi}{2}}{2\pi} = \frac{5\pi}{2} \cdot \frac{1}{2\pi} = \frac{5}{4}$$ times.

translated_unit_circle