00:04
This is problem number 19, and we're given the point with polar coordinates negative 2 pi, and we're asked to find the rectangular coordinates for this point.
00:14
So the rectangular coordinates are x and y, and to find x, we find r cosine theta, and for y, we find r sine theta, where r is negative 2 and theta is pi.
00:30
So substituting those numbers in, we have negative 2 times the cosine of pi, and negative 2 times the sign of pi.
00:43
Now at the end of the video, i'll show you how you can calculate the cosine of pi and the sign of pie without a calculator.
00:50
For now, we'll just substitute the numbers in there.
00:55
So the cosine of pi is negative 1.
00:57
So we have negative 2 times negative 1.
01:00
And the sign of pi is 0.
01:02
So we have negative 2 times 0, which gives us for our coordinates, an x coordinate of 2 and a y coordinate of 0...