High School · Similarity, Right Triangles, and Trigonometry

CCSS.MATH.CONTENT.HSG.SRT.D.9

(+) Derive the formula A = 1/2 ab sin(C) for the area of a triangle by drawing an auxiliary line from a vertex perpendicular to the opposite side.

Read this standard on the official Common Core site

Lessons that teach this standard

• Area of a Triangle from Two Sides and an Angle

  Why the area of any triangle is one half ab sin C, derived by dropping a height from a vertex, why the formula still works when the angle is obtuse, and how to use it.