<span>First of all, there should be coherence for the units of measurement -- either they are all meters or they are all ft. I would assume they are all ft.
The correct answer is 75 ft above. T
The explanation is the following: suppose the ground level is the x-axis, the 2 feet of the arch lie respectively on (0,0) and (100,0) on the ground level. Since the arch is 100ft high, the vertex of the parabola will be the point (100,100). Thus, we can find the equation describing the parabola by putting the three points we know in a system and we find that the equation of the parabola is y=(-1/100)x^2+2
To find the focus F, we apply the formula for the focus of a vertical axis parabola, i.e. F(-b/2a;(1-b^2+4ac)/4a).
By substituting a=-1/100, b=2 and c=0 into the formula, we find that the coordinates of the focus F are (100,75).
So we conclude that the focus lies 75ft above ground.</span>
The surface area of a cylinder is define by the formula S.A.=2πrh+2<span>πr^2, where the first part of the formula refers to the lateral area, perimeter, or circumference and the second part to the area of the bases, which are circles.
On this exercise it is asked to find the lateral area of a cylinder whose radius is 6 cm, and has a height of 20cm. To find the lateral area of the cylinder you should substitute this values into the formula, S.A.=2</span>πrh, and as can be seen the answers are given in terms of <span>π or pi.
S.A.=2</span><span>πrh
S.A.=2</span><span>π(6cm)(20cm)
S.A.=2</span><span>π(120cm)
S.A.=240</span>π cm^2
The lateral area of the cylinder is 240<span>π cm^2 or in other words letter B from the given choices.</span>
If only it was in english i could of read it and gave you the answer
