// minds behind maths
Leonhard Euler
1707–1783 · Mathematics
Leonhard Euler was a Swiss mathematician, one of the most prolific in history. He reshaped trigonometry by treating sine and cosine as functions of a number rather than as lengths in a particular triangle, placing them on the unit circle and tying them to the exponential function through his famous identity linking e, i, and pi. This function viewpoint is exactly what makes the unit circle, radian measure, and the sine and cosine graphs work together as they do today.
Source: Wikipedia — Leonhard Euler
Formulas that trace back to Leonhard Euler
Euler's Formula
e^(iθ) = cos θ + i sin θ
Euler's Formula & de Moivre
e^{iθ} = cos θ + i sin θ; (r(cosθ+isinθ))ⁿ = rⁿ(cos nθ + i sin nθ)
Polar Coordinates
x = r cos θ, y = r sin θ; r = √(x²+y²), θ = atan2(y, x)