I came across some interesting mistakes in many area of mathematics with my students and do not let me also to tell you for university students level, I would like to know How do i deal with students who make these mistakes :
Mistakes:
1) For $x,y >0 , \log (x+y)=\log x+\log y $
2) For $z\in {C} ,\cos²z+\sin²z \neq 1 $
3) $1 $ is a prime number because $1 $ divides $1 $ and itself
4) For $x, y \in {R},\sqrt{(x²+y²)}=x+y $
5) For $g(x)\neq 0, \displaystyle \int_{a}^{b}\frac{f(x)}{g(x)}dx=\frac {\int_{a}^{b} f(x)}{\int_{a}^{b}g(x)}dx $
6) ${0}^{\infty}$ is indeterminate case .
Some Teachers in mathematics believe that the claim 6 is true .
My question here is : How do i deal with students who make these mistakes?
Edit: I edited the question to be clear and according to the below comments
Thank you for any help !!!