(side note: your formula C = 2πr^2 is incorrect, it should be C = 2πr)
Answer:
r = 9
Step-by-step explanation:
First let's find the circumference of Circle A. To use the formula we need radius. Since we have a diameter just divide by 2 to get radius. 27 / 2 = 13.5
Now plug that into C = 2πr: 2π*(13.5) = 27π
The question says that the area of circle B is 3x this value, so Circle B's area must be: 27π * 3 = 81π
Now plug that into A = πr^2 and solve for r:
(edited to correct a brain fart)
Answer:
Step-by-step explanation:
Since the foci are at(0,±c) = (0,±63) and vertices (0,±a) = (0,±91), the major axis is the y- axis. So, we have the equation in the form (with center at the origin) .
We find the co-vertices b from b = ±√(a² - c²) where a = 91 and c = 63
b = ±√(a² - c²)
= ±√(91² - 63²)
= ±√(8281 - 3969)
= ±√4312
= ±14√22
So the equation is