# Thread: circle

1. ## circle

2. i just need to know how to start it, the second problem th answer for the slop cannot contain T and S.

3. Originally Posted by midnightwynter
i just need to know how to start it, the second problem th answer for the slop cannot contain T and S.
I've modified the first sketch a little bit.

If the center of the circle has the coordinates $C(x_C, y_C)$ then the point P has the coordinates $P(x_C+u , y_C + v)$

Use the right triangle with the legs u and v and the hypotenuse r . Then
$\color{red}v = r \cdot \sin(q)$ and
$\color{blue}u = r \cdot \cos(q)$

4. I've modified the 2nd sketch a little bit.

1. Determine the coordinates of S and T. Use the attached sketch.

2. You are supposed to know the formula to calculate the slope of a line which runs through 2 points.

If the points are $P(x_P, y_P)$ and $Q(x_Q, y_Q)$ then the slope, determined by these points, is:

$m_{PQ}=\dfrac{y_Q - y_P}{x_Q - x_P}$

5. Originally Posted by earboth
I've modified the first sketch a little bit.

If the center of the circle has the coordinates $C(x_C, y_C)$ then the point P has the coordinates $P(x_C+u , y_C + v)$

Use the right triangle with the legs u and v and the hypotenuse r . Then
$u = r \cdot \sin(q)$ and
$v = r \cdot \cos(q)$
Excuse me but I believe you have that backwards: u= r cos(q) and v= r sin(q).

6. Originally Posted by HallsofIvy
Excuse me but I believe you have that backwards: u= r cos(q) and v= r sin(q).
Of course you are right. Thanks for spotting my mistake.

I've "repaired" this accident.