Find the area $ A $ of a cone if radius $r = 4$ and slant height $l = 9$.

$A = 52\pi$

STEP 1: find base area $ AB $

To find base area $ AB $ use formula:

$$ AB = r^2 \cdot \pi $$

After substituting $ r = 4 $ we have:

$$ AB = 4^2 \cdot \pi $$ $$ AB = 16 \cdot \pi $$

STEP 2: find Curved Surface Area $ CSA $

To find Curved Surface Area $ CSA $ use formula:

$$ CSA = r \cdot l \cdot \pi$$

After substituting $ r = 4 $ and $ l = 9 $ we have:

$$ CSA = 4 \cdot 9 \cdot \pi$$$$ CSA = 4 \cdot 9 \cdot \pi $$$$ CSA = 36\pi $$

STEP 3: find area $ A $

To find area $ A $ use formula:

$$ A = AB + CSA $$

After substituting $ AB = 16\pi $ and $ CSA = 36\pi $ we have:

$$ A = 16\pi + 36\pi $$ $$ A = 16\pi + 36\pi $$ $$ A = 52\pi $$

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