Pretty please help omggg pls ill mark brainliesttt

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

Acyclist bike x distance at 10 miles per hour .and returns over the same path at 8 miles per hour.what is the cyclist average rate for the round trip in miles per hour ?

Cole says the distance between points (-5,0) and (0,-5)is 5 units. is he correct? explain why or why not.