Trigonometry

Trigonometry Formulas involving Product identities:

• $sinx\cdot cosy=\frac{sin(x+y)+sin(x-y)}{2}$
• $cosx\cdot cosy=\frac{cos(x+y)+cos(x-y)}{2}$
• $sinx\cdot siny=\frac{cos(x+y)-cos(x-y)}{2}$

G.Trigonometry Formulas involving Sum to Product Identities:

• $sinx+siny=2sin\frac{x+y}{2}cos\frac{x-y}{2}$
• $sinx-siny=2cos\frac{x+y}{2}sin\frac{x-y}{2}$
• $cosx+cosy=2cos\frac{x+y}{2}cos\frac{x-y}{2}$
• $cosx-cosy=-2sin\frac{x+y}{2}sin\frac{x-y}{2}$