00:01
Hello, let's have a look at the question.
00:02
So the question state that consider the following function.
00:06
So we have integration of x to the power 3 divided by under root 81 minus x square dx.
00:15
Now we have to determine in the a part the appropriate trigonometric substitution.
00:21
So firstly we have x is equals to 9 sine theta since the integrand contains the expression under root 81 minus x square or we can write this as under root 9 square minus x square.
00:38
So let us put the substitution here.
00:41
So we will get under root of 81 minus here we will have 9 sine theta whole square.
00:52
So this will be under root of 81 minus 81 sine square theta.
00:59
So further we can write taking in under root 81 common so we have 1 minus sine square theta.
01:07
So this will be 9 and under root of cos square theta as the value for 1 minus sine square theta is cos square theta.
01:17
So on solving we will get 9 cos theta.
01:21
So this is an appropriate substitution.
01:24
Now let us check for the second part that is x is equals to 9 tan theta.
01:32
So we have under root 9 square minus x square.
01:39
So we will get under root of 9 square minus 9 tan theta whole square.
01:48
So this will be under root of 9 square minus here we will get 9 square and tan square theta.
01:58
So taking 9 square common we have 9 square multiplied with 1 minus tan square theta.
02:07
So here this will be 9 under root of 1 minus tan square theta.
02:12
So here we see that this can't be solved further.
02:16
So this is not an appropriate substitution.
02:18
Now for the third part here we have that x is equals to 9 sec theta...