Today I took the highly scientific method of measuring it with a ruler. At an 11 cm distance from the target, I measured how much of the ruler fitted in the field of view. The result: 11.9 cm, in both 4:3 and 16:9 mode. That means the horizontal field of view (HFOV) is 56.8° (let's say ±0.5° for my precision error).

Does anyone have the official figure to confirm my measurement?

BTW, using the HFOV and the focal length (5.2 mm, according to EXIF in the pictures taken by the phone), the photo sensor horizontal size comes out as 5.6 mm. Which sounds about right