Question

помогите пожалуйста ​

Answer 1

Explicație pas cu pas:

$L = 2\pi \: r$

$A =\pi {r}^{2}$

1) r = 2,5

$L = 2\pi \: r = 2\pi \times 2.5 = 5\pi$

$A =\pi {r}^{2} = \pi(2.5)^{2} = 6.25\pi$

2)

$L = 4\pi = > 2\pi \: r = 4\pi = > r = 2$

$A =\pi {r}^{2} = {2}^{2}\pi = 4\pi$

3)

$A =\pi {r}^{2} = 64\pi \\ = > {r}^{2} = 64 = > r = 8$

$L = 2\pi \: r = 2\pi \times 8 = 16\pi$