where Q w is the weak charge, T 3 is the weak isospin, θ θ w is the weak mixing angle, and Q ϵ ϵ is the electric charge. The approximation for the weak charge is usually valid, since the weak mixing angle typically is 29° ≈ 30°, and 4 sin 2 ⁡ ⁡ 30 ∘ ∘ = 1 , and 4 sin 2 ⁡ ⁡ 29 ∘ ∘ ≈ ≈ 0.940 , a discrepancy of only a little more than 1 in 17.