a. Euler's Identity

a1. Euler's Identity (vers. 1)

a2. Euler's Identity (vers. 2)

b. Euler's Formula

b1. Euler's Formula (vers. 1)

b2. Euler's Formula (vers. 2)

c. Euler's sum of reciprocal squares

c1. Euler's sum of reciprocal squares (vers. 1)

c2. Euler's sum of reciprocal squares (vers. 2)
