How to prove that $\|x-y\| \geq |\|x\|-\|y\||$?
I am only thinking of for the LHS, $\sqrt{(x_2-x_1)^2 +(y_2-y_1)^2}$ but not sure how to manipulate that and how to handle the RHS.
How to prove that $\|x-y\| \geq |\|x\|-\|y\||$?
I am only thinking of for the LHS, $\sqrt{(x_2-x_1)^2 +(y_2-y_1)^2}$ but not sure how to manipulate that and how to handle the RHS.