Discuss the continuity of sine function.

Explanation

To discuss the continuity of the sine function, we will analyze it using the definition of continuity at a point. The sine function is defined as \( f(x) = \sin x \). We will check the continuity of this function at a point \( x = k \), where \( k \) is any real number.

### Step-by-Step Solution:

1. **Definition of Continuity**:
A function \( f(x) \) is continuous at a point \( x = k \) if:
\[
\lim_{x \to k} f(x) = f(k)
...