How do i solve circumference and areas of circles?

Which function has an inverse function? a.f(x)= |x+3|/5 b. f(x)= x^5-3 c. f(x)= x^4/7+27 d. f(x)= 1/x²

If value of cos330° is √3/2 then find tan165°.

Isaac wants the equation below to have no solution when the missing number is placed in the box. which number should he place in the box?