A trough is 10 ft long and its ends have the shape of isosceles triangles that are 3ft across at the top and have a height of 1ft. if the trough is filled with water at a rate of 12ft^3/min, how fast does teh water level rise when the water is 6inches deep? so far i have: dv/dt= 12ft^3/min and need to find dh/dt. V= base* height*length ? where length=10 ft. what i don't understand is how come in my notes, the next step is that b becomes 0.5*b*h??