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Bellows Free Academy

71 South Main Street, St. Albans, VT 05478 (get directions)

P: (802) 527-6555 • F: (802) 527-6453 (contact info)

 

The Meaning of Trigonometry

 

In the beginning.  They defined "Sine" as half the chord between two points on a circle.  The said that the length of that chord was going to be named "sine". 

Then "Cosine" was defined as the length of the side that completed the right hand triangle with the angle being half of the original.  All trig functions were created from the sine and cosine.

 

 

 

 

If the length of the radius was 1, and knowing Pythagorus' Theorem.  Do these now make sense?

Pythagorean Identities

 

Reciprocal identities 

 

 

Quotient Identities

 

Co-Function Identities

 

Even-Odd Identities