Which of the following explains why Cosine 60 degrees = sine 30 degrees using the unit circle? E2020?

Lindsay used two points, (x,y; ) and (+2.82), to find the equation of the line, y = mx + b, that passes through the points. y2-y, first, she used the definition of slope and determined that the value of mis x, - . given this information, which expression must represent the value of b?

Ill mark the brainliest if you me with the these three questions 7,8,9

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)