Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 2 - No. 10)
In the formula for the area of any triangle: Area = 1/2 * ab * sinC. If you know the area and two sides, how to find the angle?
Sine^-1 (2 * Area)/(ab)
Cosine^-1 (2 * Area)/(ab)
Area/ (0.5 * ab)
1/2ab
คำอธิบาย
Rearranging the formula to find the angle gives sin^-1 (2 * Area)/(ab).