Explanation:
without a picture here I assume the following triangle/naming structure :
a is the side opposite of vertex/angle A. it connects CB.
b is the side opposite of vertex/angle B. it connects AC.
c is the side opposite of vertex/angle C, and is the baseline. it connects AB.
b and c connect therefore at A.
the area of a triangle is
baseline × height / 2
our baseline is c = 11.863 m
the height from C to c is the sine of angle A multiplied by the radius of the trigonometric circle, which is b.
so,
height = sin(25°30') × 13.0711 = sin(25.5°) × 13.0711
25°30' = 25.5°
because one degree has 60 minutes.
height = 5.627253597... m
the triangle area is then
5.627253597... × 11.863 / 2 = 33.37805471... m²
≈ 33 m²