5. Trigonometry
-Trigonometry is a branch of mathematics that studies relationships between side lengths and angles of triangles.
-Sine, cosine and tangent are the main functions used in Trigonometry and are based on a Right-Angled Triangle.
The functions of sin, cos and tan can be calculated as follows:
Sine Function: sin(θ) = Opposite / Hypotenuse.
Cosine Function: cos(θ) = Adjacent / Hypotenuse.
Tangent Function: tan(θ) = Opposite / Adjacent
-We can find the coterminal angles of a given angle by using the following formula
:Coterminal of θ = θ + 360° × k
–The reference angle is the positive acute angle that can represent an angle of any measure.
:reference angle = 180° – angle , 180° to 270°: reference angle = angle – 180° , 270° to 360°: reference angle = 360° – angle .
–The Law of Sines (or Sine Rule) is very useful for solving triangles:
a /sin A = b/ sin B = c/ sin C
-<The law of cosines>
a, b and c are sides. C is the angle opposite side c. The Law of Cosines (also called the Cosine Rule) says: c2 = a2 + b2 − 2ab cos(C)