Can someone help me with 17 20 and especially 21 Only reply if your seriously trying to help me it would be really appreciate

Evaluate cos2θ for cosθ = square root of 3/2

The graph shows the amount of money noah earned based on the number of lawns he cut. which list shows the dependent quantities in the graph?

Charlie is at an amusement park that has 18 different rides. each ride costs $1.75. the function c(r) = 1.75r represents the total amount of money that charlie will spend if he goes on r rides, but he never goes on the same one more than once. what domain and range are reasonable for the function?