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Trigonometry

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Definitions  of Trigonometric Functions

Identities

Trigonometric Functions of Sums and Differences     

Graphs

Double Angle

Half Angle

Inverse Trigonometric Functions

Inverse Graphs

Sin and Cos Laws

Applications Page 1

Applications Page 2

Applications Page 3

Double Angles

 To understand this page, the reader need to be be familiar with the material described  in the sums and differences page.

Using the sums and differences formulas and setting Y to be X, we arrive at:

Sin2X = Sin(X + X) =

SinXCosX + CosXSinX

Sin(2X) = 2SinXCosX

Cos2X = Cos(X + X)=

CosXCosX - SinXSinX

Cos(2X) = Cos²X - Sin²X

Tan(2X) = Tan(X + X) =

(TanX + TanX)/(1 - TanXTanX)

     Tan(2X) = 2TanX/(1 - Tan²X)         

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Copyright © 2001 Trigonomerty Made Simple, Inc.
Last modified: July 24, 2001