How to solve for the sin 11pi/2 without using a calculator?

In the diagram, the ratio of ab to ae is (1/2) . what is the ratio of the length of to the length of ?

Find the value of x for which the lines are parallel.

Abouncy ball is released from a certain height. on the first bounce, it travels 32cm. with each subsequent bounce, it travels 9/10 the distance of the previous bounce. what is the total distance that the ball has traveled when it completes its 25th bounce?