Video Transcript
Determine the integral of two times the sin of π₯ divided by six with respect to π₯.
We can see the question is asking us to determine the integral of a trigonometric function. And this is the form of a standard trigonometric integral rule which we should commit to memory. For constants π and π, where π is not equal to zero, the integral of π times the sin of ππ₯ with respect to π₯ is equal to negative π times the cos of ππ₯ divided by π plus our constant of integration π.
First, in our integral, we can see weβre multiplying by two, so our value of π is equal to two. Next, we can see weβre taking the sin of π₯ divided by six. Weβll write π₯ divided by six as one-sixth times π₯. And by writing it in this way, we can see that our value of π is equal to one-sixth. So to integrate two times the sin of one over six times π₯ with respect to π₯, we just need to apply this integral rule. So by using our integral rule with π equal to two and π equal to one-sixth, we get negative two times the cos of one-sixth times π₯ divided by one-sixth plus a constant of integration π.
And we can simplify this answer. First, weβll write one-sixth times π₯ as π₯ over six. Next, instead of dividing by one-sixth, weβll multiply by the reciprocal of one-sixth. And the reciprocal of one-sixth is six. So this gives us negative two times six times the cos of π₯ over six plus π. And we can simplify negative two times six to give us negative 12. Therefore, weβve shown the integral of two times the sin of π₯ over six with respect to π₯ is equal to negative 12 times the cos of π₯ over six plus π.