Geometric Proof of the Double Angle Cosine Formula
2020-04-10 02:07
This GeoGebra example demonstrates the geometric proof of the double angle cosine formula cos(2α) = cos²α - sin²α. Using geometric constructions including circles, rays, angles, perpendicular lines, and reflections, it visually illustrates the trigonometric relationship between double angles and single angles. Through precise constructions of intersections, segments, and angles, it helps learners
In collections
Secondary Vocational Mathematics
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∴\cos2α=OD=OA-AD=1-2\sin^2α\\
=1-2(1-\cos^2α)=2\cos^2α-1\\
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