simp only [add_im, int_cast_im, mul_im, int_cast_re, MulZeroClass.zero_mul, add_zero, zero_add]
a b c : ℤα
⊢ (↑a.z + ↑a.w * { re := 1 / 2, im := rt7 / 2 }).im = ↑a.w * rt7 / 2
a b c : ℤα
⊢ ↑a.w * (rt7 / 2) = ↑a.w * rt7 / 2