Write a proof to prove them, please only number 9

If sec theta = 5/3 and the terminal point determined by theta is in quadrant 4, then

Which expression demonstrates the use of the commutative property of addition in the first step of simplifying the expression (-1+i)+(21+5i)+0

Apiling for a high-rise building is pushed by two bulldozers at exactly the same time. one bulldozer exerts a force of 1250 pounds in a westerly direction. the other bulldozer pushes the piling with a force of 2650 pounds in a northerly direction. what is the direction of the resulting force upon the piling, to the nearest degree? a. 65 n of w b. 25 n of w c. 45 n of w d. 35 n of w