Derive an expression for the magnetic induction in the center of the triangular loop with current.

Formula designations:
1. L and M – own and mutual inductance;
2. di – current filaments;
3. dl – elements of the length of the threads;
4. Ө – angle between elements;
5. μ0 – magnetic constant.
Formulas:
1. L = 1 / i ^ 2∫di∫М * di;
Let’s transform:
2. M = 1 / i1i2∫di∫M * di;
We get:
3. M = (μ0 / 4п) ∫∫ (dl * dl) / L * cos Ө.
Answer: M = (μ0 / 4p) ∫∫ (dl * dl) / L * cos Ө.