H (1/2)(z)=sqrt(2/(pi z))(1-cos(z))
From specialfunctionswiki
Theorem
The following formula holds: $$\mathbf{H}_{\frac{1}{2}}(z) = \sqrt{\dfrac{2}{\pi z}}(1-\cos(z)),$$ where $\mathbf{H}_{\frac{1}{2}}$ denotes a Struve function, $\pi$ denotes pi, and $\cos$ denotes cosine.
Proof
References
- 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $12.1.16$