Evaluate L 0 cos nx L cos mx L dx for n 0, m 0. Use the trigonometric identity cos a cos
Chapter 2, Problem 2.3.6(choose chapter or problem)
Evaluate L 0 cos nx L cos mx L dx for n 0, m 0. Use the trigonometric identity cos a cos b = 1 2 [cos(a + b) + cos(a b)] . (Be careful if a b = 0 or a + b = 0.)
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