A relation \( R = \{(a, b) : a = b - 2, b \geq 6 \} \) is defined on the set \( \mathbb{N} \). Then the correct answer will be:
The principal value of the \( \cot^{-1}\left(-\frac{1}{\sqrt{3}}\right) \) will be:
Prove that the \( f(x) = x^2 \) is continuous at \( x \neq 0 \).