



 
Hi Mac, Here is what I see.
h is the height of the triangle, b is the length of the base and is the angle at the apex of the triangle. All three of these quantities are functions of time t. You know the rate of change of at a particular time and you want to know the rate of change of A, the area of the triangle, at the same time. The rate of change is the derivative with respect to t so you are going to have to find a relationship between and A. The area of a triangle is half the base times the height so
From the diagram b/2 = 3.5 sin(/2) and h = 3.5 cos(/2). Thus
You can now differentiate both sides with respect to t to find a relationship among A'(t), (t) and '(t). At the time when the triangle is equilateral (t) = /3 radians and '(t) = 1/3 radians per second so you can solve for A'(t). Before you start however, do you know a trig identity that will simplify the expression for A? Penny  


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