How to do 28a ? Thanks

If sr is 4.5cm and tr is 3cm, what is the measure in degrees of angle s?

1- what do you think the product of a nonzero rational number and an irrational number is? is it rational or irrational? make use of variables, the closure property of integers, and possibly a proof by contradiction to prove your hypothesis.2- why do we have to specify that the rational number must be nonzero when we determine what the product of a nonzero rational number and an irrational number is? if the rational number were 0, would it give us the same result we found in the first question?

What is the value of the expression i 0 × i 1 × i 2 × i 3 × i 4? 1 –1 i –i