Page 76 - How To Solve Word Problems In Calculus
P. 76
3.
B
y
z
70
x
A
dx dy
Given: = 25 = 45
dt dt
dz
Find: 2 hours later
dt
The relationship between x and y is easily obtained if we look at the
diagram just the right way.
z
x + y
x
70
2
2
2
By the theorem of Pythagoras, z = (x + y) + 70 . Differentiating,
dz dx dy
2z = 2(x + y) + + 0
dt dt dt
dz dx dy
z = (x + y) +
dt dt dt
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