Common Core Math - HS Geometry
Lesson Plan
Derive triangle area formula
Goals / Objectives
Derive the formula A = (1/2)ab sin(C) for the area of a triangle by drawing an auxiliary altitude from a vertex perpendicular to the opposite side
Explain why the formula works for acute, right, and obtuse triangles
Apply the formula to find the area of a triangle given two sides and the included angle
Recognize when to use A = (1/2)ab sin(C) versus the base-height formula
Interpret the role of sin(C) geometrically - how the included angle controls area for fixed side lengths
Use the formula to solve real-world problems involving triangular regions
Standards
HSG.SRT.D.9
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.
Academic Vocabulary
Not in our source material
Materials
Remediation
Enrichment
Accommodations
Not in our source material
Anticipatory Set / Bell Work
Modeling
Check for Understanding
This lesson’s brief has no Formative Assessment or Assessment Ideas