A skateboarder is attempting to skate through a vertical loop of radius r = 7.5 m. He skates down a ramp and is launched into the loop by an inclined plane that makes an angle of = 45 degrees with respect to the horizontal.

If the skateboarder begins from rest how high does the ramp he starts from have to be so that he does not fall at the top of the loop? Give your answer in meters.

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