**Trigonometry Formulae: Don’t try to remember just know the concept of derivation**

**With the help of sin (A + B), we can derive all the remaining trigonometric formulae. Let’s see, how …..**

**Compound Angle**

(1)

(2)

(3)

(4)

(5)

**Dividing Numerator and Denominator** by

(6)

**Similarly,**

(7)

(8)

**Transformation Formulae:**

**By adding (1) and (2), we get**

(9)

**By subtracting (2) from (1), we get**

(10)

**By adding (3) and (4), we get**

(11)

By subtracting (4) from (3), we get

(12)

Now, consider and

Then, and

(13) **From (9),**

(14) **From (10),**

(15) **From (11),**

(16) **From (12),**

**Multiply (1) and (2), we get**

(17)

(18)

**Multiple Angles**

(19)

(20)

(21)

(22)

(23)

(24)

**From (20),**

And

(25)

(26)

(27)

(28)

**Half Angles**

**From (25),**

(29)

(30)

(31)