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.
The strategy we adopt in solving trigonometric equations is to find one solution using knowledge of commonly occurring angles and then use the symmetries in the graphs of the trigonometric functions to deduce additional solutions. Video tutorial 44 mins.