Press space or use the arrow keys to change slides and enjoy! Have you ever seen a lunar eclipse? Tell me about it in the comments! Note: During the mathematical explanation of how often eclipses occur, some concepts are introduced and not much is said about them. Here are some short explanations. Triangle Sum Theorem: If you have the measures of two angles in a triangle, you can find the third by subtracting those two measures from 180°. Law of Sines: The sine of an angle over the length of its opposite side is equal to the sine of any other angle over the length of its opposite side. Opposite Side: The side of a triangle that is not adjacent to/makes up an angle. Leg: One of the sides of a right triangle that is adjacent to the right angle. Sine: The length of the opposite side divided by the hypotenuse of a right triangle. 6/4/18: Featured?!? Oh my gosh! This is insane! Thanks for all the awesome comments detailing your eclipse experiences! However, I may not be able to respond to all of them, but I'll do my best! Also, please refrain from advertising here. Any and all advertisement comments will be deleted.