10. The altitude of a building is 40 m. How far are you from the base of the building, if the angle
of elevation from the ground to the top of the
building is 50°
40 m
50°

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )