To find the area that the sprinkler can spray, we need to consider that it operates over a half-circle (180°) with a radius of 15 feet.
The formula for the area of a circle is given by:
\[ A = \pi r^2 \]
Since the sprinkler only sprays over half of a circle, we will take half of this area.
- Calculate the area of a full circle with radius 15 feet:
\[ A_{full} = \pi (15)^2 = \pi \cdot 225 = 225\pi \text{ ft}^2 \]
- To find the area for a half-circle:
\[ A_{half} = \frac{1}{2} A_{full} = \frac{1}{2} (225\pi) = 112.5\pi \text{ ft}^2 \]
Therefore, the area of the backyard that the sprinkler can spray is:
\[ \boxed{112.5\pi \text{ ft}^2} \]