# Thread: Help? Parametric and circle questions

1. ## Help? Parametric and circle questions

1. Find two different parametric descriptions for he circle of radiu 4 centered at (-3, 2).

2. The radius of the circumscribed circle of the triangle ABC is 15 cm. Given that B is a 49-degree angle, find the length of side AC.

2. 1. A circle of radius 4 centered at (-3, 2) has the equation $\displaystyle (x + 3)^2 + (y - 2)^2 = 16$. However, you can use trigonometric functions to establish a circular path with center (h, k) and radius r:

$\displaystyle x = h + r \sin t$
$\displaystyle y = k + r \cos t$

or

$\displaystyle x = h + r \cos t$
$\displaystyle y = k + r \sin t$.

The first represents a clockwise path, and the second represents a counterclockwise path.

3. Hello, pyrosilver!

2. The radius of the circumscribed circle of the $\displaystyle \Delta ABC$ is 15 cm.
Given that $\displaystyle \angle B = 49^o$, find the length of side $\displaystyle AC.$
Code:
                A
* o *
*    /*\    *
*     / * \     *
*     /  *  \     *
/ 15*   \
*    /    *    \    *
*   /    Po 98° \   *
*  /         *   \  *
/ 49°      15 * \
B o - - - - - - - - o C
*               *
*           *
* * *

The center of the circle is $\displaystyle P$.

Draw radii $\displaystyle PA = PC = 15$

Since inscribed angle $\displaystyle ABC = 49^o$, then central angle $\displaystyle APC = 98^o$

Use the Law of Cosines on $\displaystyle \Delta APC.$