Answer:
10
Explanation:
Use Pythagorean theorem,
Base² + altitude²= hypotenuse²
8² + altitude² = (2√41)²
64 + altitude² = 2²*(√41)² {(√41)² = √41*√41 = 41}
64 +altitude² = 4 * 41
64 +altitude² = 164
altitude² = 164 - 64
altitude² = 100
altitude = √100 = 10