Polar Coordinates #4

In the coordinate (r, theta), r stands for the radius. If theta>0, then you rotate counterclockwise. If theta<0, then you rotate clockwise. When converting from polar (r, theta) to rectangular (x,y), substitute x=rcostheta and y=rsintheta. When converting from rectangular to polar, substitute r^2=x^2+y^2 and tan(theta)=y/x. For both of these conversions, solve for x or r. Trig identities are also key to this process.

Rotating Conic Sections #3

The starting point for rotating conic sections is to use the formula Ax^2+Bxy+Cy^2+Dx+Ey+F=0. Identify all parts in order to being step 1. The first step is to find the angle using cot2(theta)=(A-C)/B. Step two is to replace x and y with either x=x'cos(theta)-y'sin(theta) or y=x'sin(theta)+y'cos(theta). The final step is to use algebra and simplify! A helpful hint is to use the different trig identities used previously so it will be easier to replace things. Rotating conic sections can be tricky, but the trickiest part is to not mess up on the basic algebra steps.

Parabolas #2

Parabolas are U shaped graphs. They have a focus, which is right above the vertex and that distance is called c and is (h,k+c) . The vertex is the center of the parabola such is (h,k). The directrix is y=k-c and is the line below the vertex. The parts described are for a graph that has a c>0, or positive. If the c<0, or negative, then the parts are reversed. The basic equation for a positive parabola is (x-h)^2=4c(y-k) and the basic equation for a negative parabola is (y-k)^2=4c(x-h).