The Computer Graphics Companion Online Edition

Damian Scattergood 1999-2001

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TRIGONOMETRY

PI - p

p being an irrational number.

where p = 3.1415926535897....

The current value of PI has been calculated to over 100,000 decimal places and

has proved to be endless.

· Calculation of PI.

PI can be calculated using an approximation of

RADIAN MEASURE

Definition:

The Angle subtended at the centre of a circle by an arc

equal in length to the radius has a measure of 1 radian.

By definition:

PYTHAGORAS'S THEOREM

Pythagoras's Theorem states that the square of the Hypotenuse (AB) is equal to the sum of the
squares of the other two sides, (AC) and (BC).

For a given right angle triangle

TRIANGLE FORMULAS - 2D

Hypotenuse = Opposite / SIN (Angle) = Adjacent / COS (Angle)

Adjacent = Hyponetuse * COS (Angle) = Opposite / TAN (Angle)

Opposite = Hypotenuse * SIN (Angle) = Adjacent * TAN (Angle)

SIN (Angle) = Opposite / Hyponetuse

COS (Angle) = Adjacent / Hypotenuse

TAN (Angle) = Opposite / Adjacent

COT (Angle) = Adjacent / Opposite

SEC (Angle) = Hypotenuse / Adjacent

CSC (Angle) = Hypotenuse / Opposite

TRIANGLE FORMULAS - 3D

NOTES

Signs:=

Angle A

sin A cos A tan A cot A sec A csc A

0°

0

1

0

± ¥

1

± ¥

90°

1

0

± ¥

0

± ¥

1

180°

0

-1

0

± ¥

-1

± ¥

270°

-1

0

± ¥

0

± ¥

-1

Angle A

sin A cos A tan A cot A sec A csc A

30°

½

½Ö 3

1/3Ö 3

Ö 3

2/3Ö 3

2

45°

½Ö 2

½Ö 2

1

1

Ö 2

Ö 2

60°

½Ö 3

½

Ö 3

1/3Ö 3

2

2/3Ö 3

ADDITION FORMULAS.

sin (a+b) = sin a * cosb+cos a*sin b

cos (a+b) = cos a * cos b- sin a*sin b

tan (a+b) = tan a + tan b

1-tan a * tan b

SUBTRACTION FORMULAS.

sin (a-b) = sin A * Cos B - Cos A * Sin B

cos (a-b) = Cos A * Cos B + Sin A * Sin B

tan (a-b) = tan A - Tan B

1 + Tan A * Tan B

Double Angle Formulas:

Sin 2A = 2 Sin A * Cos A

Cos 2A= Cos^2A - Sin ^2A = 1-2Sin ^2A = 2Cos^2A -1

Tan 2A = 2TanA

1-Tan^2A

PRODUCTS

SUM AND DIFFERENCE

1