The angle of lens is decision illuminate direction, we can calculate illuminate area with tangent function.

Trigonometric  Function  Of  Acute Angle

tan10°=0.176（can calculate that lens value as 20°）
tan12.5°=0.222（can calculate that lens value as 25°）
tan15°=2-√3
tan22.5°=√2-1
tan30°=√3/3
tan45°=1
tan60°=√3

Different angle , different aperture and illuminate value

30°
1meter aperture φ0.56M illuminate area as 0.246 square   metres
2meter aperture φ1.12M illuminate area as 0.985 square metres
3meter aperture φ1.68M illuminate area as 2.217 square metres
45°
1meter aperture φ0.828M illuminate area as 0.538 square metres
2meter aperture φ1.656M illuminate area as 2.154 square metres
3meter aperture φ2.484M illuminate area as 4.864 square metres
60°
1meter aperture φ1.15M illuminate area as 1.046 square metres
2meter aperture φ2.3M illuminate area as 4.189 square metres
3meter aperture φ3.46M illuminate area as 9.424 square metres
120°
1meter aperture φ3.464M illuminate area as 9.424 square metres
2meter aperture φ6.928M M illuminate area as 37.697square metres
3meter aperture φ10.392M illuminate area as 84.818 square metres