1. Maths 3, 4: Trigonometry
Identities & Formulas - 1
1. Trigonometric Functions of Acute Angles
sin X = a / c
csc X = c / a Important!
tan X = a / b
cot X = b / a
cos X = b / c
sec X = c / b
2. Special Triangles
2. Maths 3, 4: Trigonometry
Identities & Formulas - 2
Special triangles may be used to find trigonometric functions of
special angles: 30, 45 and 60 degress.
3. Sine and Cosine Laws in Triangles
1 - The sine law
sin A / a = sin B / b = sin C / c
2 - The cosine laws
a 2 = b 2 + c 2 - 2 b c cos A
b 2 = a 2 + c 2 - 2 a c cos B
c 2 = a 2 + b 2 - 2 a b cos C
4. Relations Between Trigonometric Functions
cscX = 1 / sinX, sinX = 1 / cscX
secX = 1 / cosX, cosX = 1 / secX
5. Maths 3, 4: Trigonometry
Identities & Formulas - 5
14.Multiple Angle Formulas
sin(3X) = 3sinX - 4sin 3X
cos(3X) = 4cos 3X - 3cosX
sin(4X) = 4sinXcosX - 8sin 3XcosX
cos(4X) = 8cos 4X - 8cos 2X + 1
15.Half Angle Formulas
sin (X/2) = + or - SQRT [ (1 - cosX) / 2 ]
cos (X/2) = + or - SQRT [ (1 + cosX) / 2 ]
tan (X/2) = + or - SQRT [ (1 - cosX) / (1 - cosX) ]
= sinX / (1 + cosX) = (1 - cosX) / sinX
16.Power Reducing Formulas
sin 2X = 1/2 - (1/2)cos(2X))
cos 2X = 1/2 + (1/2)cos(2X))
sin 3X = (3/4)sinX - (1/4)sin(3X)
cos 3X = (3/4)cosX + (1/4)cos(3X)
sin 4X = (3/8) - (1/2)cos(2X) + (1/8)cos(4X)
cos 4X = (3/8) + (1/2)cos(2X) + (1/8)cos(4X)
sin 5X = (5/8)sinX - (5/16)sin(3X) + (1/16)sin(5X)
cos 5X = (5/8)cosX + (5/16)cos(3X) + (1/16)cos(5X)
sin 6X = 5/16 - (15/32)cos(2X) + (6/32)cos(4X) - (1/32)cos(6X)
cos 6X = 5/16 + (15/32)cos(2X) + (6/32)cos(4X) + (1/32)cos(6X)
17.Trigonometric Functions Periodicity
sin (X + 2Pi) = sin X , period 2Pi
cos (X + 2Pi) = cos X , period 2Pi
sec (X + 2Pi) = sec X , period 2Pi
csc (X + 2Pi) = csc X , period 2Pi
6. Maths 3, 4: Trigonometry
Identities & Formulas - 6
tan (X + Pi) = tan X , period Pi
cot (X + Pi) = cot X , period Pi
18. Graphs of The Six Trigonometric Functions.
Sine Function : f(x) = sin (x)
Cosine Function : f(x) = cos (x)
Tangent Function : f(x) = tan (x)