What innovation helped expand the empire and increase trade?

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

An investment decreases in value by 30% in the first year and decreases by 40% in the second year. what is the percent decrease in percentage in the investment after two years

Karen will divide her garden into equal parts. she will plant corn in 8/12 of the garden. what is the lowest number of parts she can divide her garden into?