Some FUN Facts about Trigonometry

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Formulas
The Relation between a Chord and a Tangent Line
The Law of Sines and the Unit Circle
A Geometric Proof of the Law of Sines (acute angle)
A Geometric Proof of the Law of Sines (obtuse angle)
A Geometric Proof of the Double Angle Sin Formula
A Geometric Proof of the Double Angle Cos Formula
A Circle and Trig Values
Ptolemy's Theorem and How It's Used
   Geometric Proof of the Addition Formula for the Sine Function
   Geometric Proof of the Difference Formula for the Sine Function
   Geometric Proof of the Sin*Sin + Cos*Cos = 1