Why do we need to learn trigonometry?
We need to understanding trigonometry. What is the definition of radian? What is the relationship between radian and degree? How to calculate the arc length of a circle? What is the definition of trigonometry functions? What are the four quadrant? What is the definition of positive angles and negative angles? What are the values of special angle of trigonometry function? How to find the values of a trigonometry functions of any angle? What is the period function? How to draw a period function? What is the phase shift? What is the standard sine function? How to make sine function transformation? What is the standard cosine function? How to make cosine function transformation?