Answer:
The solution is in the attached file below
4/5 is the slope. When you isolate the y on one side of a linear equation, whatever number is with the x value is your slope.
Let r be a radius of a given circle and α be an angle, that corresponds to a sector.
The circle area is

and denote the sector area as

.
Then

(the ratio between area is the same as the ratio between coresponding angles).

.
Step-by-step explanation:
Lines that are tangent to a circle are perpendicular to the radius of the circle.
Lines that are tangent to a circle are congruent
Answer:
Yi Xing invented the astronomical clock and introduced some new methods of interpolation in mathematics.
Step-by-step explanation:
Yi Xing was both an astronomer and a mathematician during the era. He invented the astronomical clock which was more accurate than the initial water and Sun's clock in use.
Furthermore, Yi Xing also discovered some new methods of interpolation in mathematics of which the meaning and interpretation became controversial. Interpolation is a method majorly in mathematics that can be used to estimate a value of a function from its discrete values. It involves first order differences and second order differences.
Also, Yi Xing was able to design a calendar in A.D. 727.