Hello, rawkstar!

This one takes a bit of work.

Hope you're sitting down . . .

Code:

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The center of the circle is

. . And: .

Let

. . Note that: .

Let , the distance he rows.

Let , the distance he walks.

Find the distance

In isosceles triangle

Use the Law of Cosines:

. .

. .

. .

He rowed miles at 2.9 mph.

. . This took: . hours.

Find the distance

The arc length is: .

Hence: .

He walked miles at 4 mph.

. . This took: . hours.

The total time is: .

And *that* is the function you must minimize.

*Go for it!*