Trigonometry

tan θ	= sin θ / cos θ	("tangent")
sec θ	= 1 / cos θ	("secant")
cosec θ	= 1 / sin θ	(or csc, "cosecant")
cot θ	= 1 / tan θ	("cotangent")
sin²θ+cos²θ	= 1
cos(θ+φ)	= cos θ cos φ - sin θ sin φ	(use e^iθe^iφ=e^i(θ+φ))
sin(θ+φ)	= cos θ sin φ + sin θ cos φ	(--"--)