[填空题]
William Tell must split the apple atop his ejw s1g3 7k0zyson's head from a distance h) dfm3 0ehpta+kf2 .xof 27 m . When William f2 dk+a)em3htx0f.phaims directly at the apple, the arrow is horizontal. At what angle must he aim it to hit the apple if the arrow travels at a speed of 35$ \mathrm{~m} / \mathrm{s}$ ? $^{\circ} $
