Sine and cosine (and trigonometric functions in general) are used extensively in physics, and neither really has priority - it depends on the particular problem you're working on. Is there a particular problem that prompted your question?
Answer: a square root of a number is a value that when multiply by itself, it gives number. Ex: 2 x 2 = 4 so 2 is a square root of 4.
64%= .64
.64 of 55= 35.2
So the length of its tail is 35.2in.