Question

Prompt Describe how you would convince a friend that sin(x + y) does not equal sin x + sin y.

Answer 1

Answer:

Let's start first with sin(x+y) :

• sin(x+y)
• sin(x)*cos(y)+cos(x)*sin(y)

Now with sin(x)+sin(y) :

• sin(x)+sin(y)
• 2*sin[(x+y)/2] * cos[(x-y)/2]

We can see that both expressions are far away from being equal