Let $r \ge 2$. How to prove that the fundamental group $\pi_1(GL_r(\mathbb{C}))$ of the invertible matrices $GL_r(\mathbb{C})$ over $\mathbb{C}$ equals $\mathbb{Z}$.
What about $\pi_1(GL_r(\mathbb{R}))$?
Let $r \ge 2$. How to prove that the fundamental group $\pi_1(GL_r(\mathbb{C}))$ of the invertible matrices $GL_r(\mathbb{C})$ over $\mathbb{C}$ equals $\mathbb{Z}$.
What about $\pi_1(GL_r(\mathbb{R}))$?