Calculus II · Techniques of Integration

Trigonometric Integrals — Practice Problems and Worked Solutions

Power identities turn trig products into integrable forms.

The formulas you need here

Power-reduction identities

What it says
An even power of sine or cosine trades itself for a single cosine of double the angle.
When to reach for it
Even powers of sine or cosine, where no substitution presents itself.
Watch out
Only the cosine version carries the plus sign. Getting them the wrong way round flips the answer.

The identity turned an unintegrable square into two standard terms.

Odd trig powers

What it says
Split off one factor to become du, and convert everything else to the other function.
When to reach for it
At least one of the two powers is odd.
Watch out
Peel from the odd one. Peeling from the even power leaves you with a square root you cannot substitute.

u = cos x, and the peeled sin x supplied the du.

16 worked problems

Every step is generated and checked by a computer algebra system.

  1. 1.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  2. 2.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  3. 3.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  4. 4.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  5. 5.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  6. 6.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  7. 7.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  8. 8.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  9. 9.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  10. 10.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  11. 11.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  12. 12.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  13. 13.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  14. 14.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  15. 15.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution
  16. 16.

    Evaluate the trigonometric integral.

    Answer:

    Step-by-step solution

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