To draw a sketch of the right triangle mentioned in the problem, follow these steps:
1. Start by drawing a straight line segment as the base of the triangle. Label the endpoints as A and B.
2. At point A, draw a perpendicular line segment upwards. Mark the length of this segment as 4cm.
3. At point B, draw a perpendicular line segment as well, but longer than the segment at point A. Mark the length of this segment as 8cm.
4. To complete the triangle, draw a line segment connecting the endpoints of the two perpendicular segments (from points A to B).
5. Finally, label the hypotenuse, which connects point A to point B, with a length of 10cm.
After completing these steps, you should have a sketch of a right triangle with the correct measurements indicated on it.