# Trigonmetrical Functions

### - formulae for Sine (sin), Cosine, (cos) and Tangent (tan)

### In this section

Trigonometrical functions, sin, cos, tan and others are widely used in the design, development, and analysis of radio and electronics circuits, as well as in other applications such as antennas, and RF components.

These trignometric relationships are widely used in the design and development of many RF and other radio circuits. In particualr sin, cos and tan are the most widely used.

The fact that their use is embedded inth e very basics of electronics and radio technology is demonstrated by the fact that a single frequency repetitive waveform is known as a sine wave because of the fact that its waveform follows the values mapped out by the sine function.

**sin (A + B) = sin (A) . cos (B) + cos (A) . sin (B)**

**cos (A + B) = cos (A) . cos (B) - sin (A) . sin (B)**

**sin (A - B) = sin (A) . cos (B) - cos (A) . sin (B)**

**cos (A - B) = cos (A) . cos (B) + sin (A) . sin (B)**

**sin (2A) = 2 . sin (A) . cos (A)**

**cos (2A) = cos^2 (A) - sin^2 (A) = 1- 2 sin^2 (A) = 2 cos^2 (A) - 1**

**sin^2 (A) + cos^2 (A) = 1**

**1 + tan^2 (A) = sec^2 (A)**

**1 + cot^2 (A) = cosec^2 (A)**

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