Curated OER
Etc: Maps Etc: United States Standard Time Belts, 1901
A map from 1901 showing the Standard Time Belts in the contiguous 48 states as they were then established. "The main body of our country is so broad from east to west that more than three hours are required for rotation to carry it past...
Wolfram Research
Wolfram Math World: Perpendicular Vectors
Come to this site to find the transformational matrix to find the vector rotated 90 degrees from the original. The site also states the special relationship between two perpendicular vectors when using the dot product.
Texas Instruments
Texas Instruments: Rotations in the Coordinate Plane
It is important for students to know what happens to the coordinates of points when they are rotated in the coordinate plane by 90 or 180 degrees, either clockwise or counterclockwise. This activity enables students to use Cabri Jr. to...