Page 152 - Calculus Workbook For Dummies

136 Part III: Differentiation

15. Two lines through the point (1, –3) are tan- 16. The Earth has a radius of 4,000 miles. Say
2
gent to the parabola y = x . Determine the you’re standing on the shore and your eyes
points of tangency. are 5’ 3.36” above the surface of the water.
How far out can you see to the horizon
Solve It before the Earth’s curvature makes the
water dip below the horizon? See the fol-
lowing figure.

You Your line of site to horizon
Horizon

x 2 + y 2 = 4000 2

Note: not drawn to
scale — you would
Earth be way smaller.
Solve It