Trigonometric Area Formula for Trapezoids
In any right triangle formed by dropping the altitude from the top vertex of leg $c$ to the base, the sine function connects the opposite side (height $h$), the hypotenuse (leg $c$), and the angle $\alpha$:
sin(α) = Opposite / Hypotenuse = h / c
h = c × sin(α)
h = c × sin(α)
Substituting $h = c \sin(\alpha)$ into the standard trapezoid area formula gives:
Area = ½ × (a + b) × c × sin(α)