Slide 1 of 9, An image of a right angled triangle. The right angle is the top left vertex of the triangle. The bottom left vertex has been labelled as seventy two degrees.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. What is a triangle? We all know that a triangle is a three-sided shape — 1, 2, 3 sides. A ...

But right now, millions of people all over the world are thinking about this very problem. Determining how to safely reopen buildings and public spaces under social distancing is in part an exercise ...