How to find surface area for a triagle

rstand how to find Surface Area and Volume of the shapes

have done the calculus which reveals that the surface area is at a minimum when height is double the radius. I am now trying to find an equation for the relationship between the amount of wasted surface area as a percentage of the minimum surface area and the ratio between height and radius. If I were to plot it on a graph, the y axis would be the percentage of excess materials needed as a percentage of the minimum possible surface area, and the x axis would be height divided by radius. Since the surface area is minimized when height=2(radius), I know that when x=2, y=0. The website https://www.datagenetics.com/blog/august12014/index.html explains what I am trying to do quite well and shows the graph below. I am trying to find the equation for this graph, but am unsure how to go about it.

ction between the floor and book is µk. Using the information given in the figure: (a) draw free body diagrams for both the books, and also for the combined system (of mass m1+m2), (b) find acceleration of the books along horizontal direction, and (c) find the magnitude and direction of the force exerted by the left book on the right book. 3.A car of mass 1500-kg enters a circular path at point P and leaves at point Q (see the figure) at constant speed of 5.0m/s, and the frictional force acting on its tires is 2500-N. a) how long it takes to reach point Q from point P, and b) what should be the minimum value of the coefficient of static friction between the tires and the road? 4)In an elevator which is accelerating downward at 2.5ms−2 , a 25-kg block hangs from a spring attached to the ceiling of the elevator. If spring gets stretched by 0.15m, find its spring constant.

variables). The answer is 8 pi r squared - 10pi r, but I'm not sure how they got the 10 pi r I only was able to get 8 pi r squared