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A Visual Proof of the Double-Angle Formula for Sine
The double-angle formula for sine states that
. Computing the area of a triangle using the formula
(area equals one-half base times height) gives
for the top triangle and
for the bottom triangle.
Contributed by:
Chris Boucher
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DETAILS
This image is from J. D. Currie, "Proof without Words: Double Angle Formula via Area,"
Mathematics Magazine
,
81
(1), 2008 p. 62.
RELATED LINKS
Double-Angle Formulas
(
Wolfram
MathWorld
)
PERMANENT CITATION
"
A Visual Proof of the Double-Angle Formula for Sine
" from
the Wolfram Demonstrations Project
http://demonstrations.wolfram.com/AVisualProofOfTheDoubleAngleFormulaForSine/
Contributed by:
Chris Boucher
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