49 Yuzi 121 cm² bo'lgan doira radiusini toping.

Doira yuzining formulasi:

\( A = \pi r^2 \),

bu yerda \( A \) — doira yuzi, \( \pi \) — son, \( r \) — radius.

Berilgan:

• Yuzi \( A = 121\pi \text{ sm}^2 \).

Radiusni topish uchun formulani o'zgartiramiz:

\( r^2 = \frac{A}{\pi} \)

\( r = \sqrt{\frac{A}{\pi}} \)

Hisoblash:

\( r^2 = \frac{121\pi \text{ sm}^2}{\pi} \)

\( r^2 = 121 \text{ sm}^2 \)

\( r = \sqrt{121 \text{ sm}^2} \)

\( r = 11 \text{ sm} \)

Ответ: Doira radiusi \( 11 \text{ sm} \).