Respuesta :

3∅ can be rewritten as (2∅+∅)
sin(3∅) = sin(2∅ + ∅)
Opening brackets on the right hand side;
 = sin2
∅ cos ∅ + cos2∅sin
This simplifies to;
 = 2sin
∅cos^2∅ + sin∅ (1- 2sin^2∅)
 = sin
∅ (2cos^2∅ + 1 - 2sin^2∅)
 = sin
∅ (2(1 - sin^2∅) +1-2sin^2∅)
 = 3sin
∅ - 4sin^3

First of all:-

3∅ can be called (2∅+∅)
so, sin(3∅) = sin(2∅ + ∅)
Open brackets on the RHS (right hand side)
 = sin2
∅ cos ∅ + cos2∅sin
This is simplified into;
 = 2sin
∅cos^2∅ + sin∅ (1- 2sin^2∅)
 = sin
∅ (2cos^2∅ + 1 - 2sin^2∅)
 = sin
∅ (2(1 - sin^2∅) +1-2sin^2∅)
 = 3sin
∅ - 4sin^3∅