Euler’s formula

Euler’s formula states complex

𝑒 𝑖 𝜃 = c o s 𝜃 + 𝑖 s i n 𝜃

giving a convenient notation for denoting complex numbers radially. It follows

c o s 𝜃 = 12 (𝑒 𝑖 𝜃 + 𝑒 - 𝑖 𝜃) s i n 𝜃 = 1 2 𝑖 (𝑒 𝑖 𝜃 - 𝑒 - 𝑖 𝜃)

Proof

proof