Pythagoras' Theorem and pizzas? The theorem is meticulously described here with an animation and extension material that brings the concept to real life (yes, using pizzas!). Among various other sections covered are sine, cosine, tangent and measurements in radians.

Radian measure

Most people usually learn to measure an angle in degrees. But in many scientific and engineering calculations radians are used in preference to degrees. Video tutorial 24 mins.