25.7.4 Area Formulas for a Triangle
Core ideaWith two sides and the angle between them, the area is ½·ab·sinC, where the sine turns 'how wide the angle opens' into area.
Module goal. We extend trig functions from the right triangle to any triangle, using the two great laws to convert freely between sides and angles, wrapping up this stage and handing the next, Sequences, a foundation of measurable relationships.