Today's soundtrack is *Tim Hicks: New Tattoo*.

I'm going on to the next lesson of trigonometry on Khan Academy this afternoon.

From the Pythagorean theorem, we know that h² = the square of the sum of the other two sides - which could be thought of as h² = o² + a² (hypotenuse² = opposite² plus adjacent²). So if we knew that in a right triangle one side was 7" and the other was 4", we could find the length of the hypotenuse like this: 7² + 4² = h²; 49+16=65; so h = square root of 65 (approximately 8").

Triangles always have 180 degrees when we add up the degrees of all of their angles.