Please answer number 17 please

Find the magnitude, correct to two decimal places, made by each of the following with positive direction of the x axis a) y= x the answer is 45° but i don’t know how

The functions f(x) and g(x) are shown in the graph f(x)=x^2 what is g(x) ?

Betty correctly answers 30 questions on your math test there are 40 questions on the test what percent of the questions did she answered incorrectly