Sine an cosine are functions which tells you what your coordinates are when you travel around a circle (of diameter 1) so anything containing those (here hidden

Sine an cosine are functions which tells you what your coordinates are when you travel around a circle (of diameter 1) so anything containing those (here hidden in Euler's formula) will provoke thinking in terms of circles. I find it very useful btw. Once you realize sin(x) represents how high you are on a circle and cos(x) how far to the right (if you start walking on it from [0,1] counter clockwise) then a lot of stuff start making intuitive sense.