Step 1: Solve integral 2.1.
We need to evaluate ∫a3xsin(2x)dx.
This integral requires integration by parts twice. We can use the formula for ∫ekxsin(mx)dx=k2+m2ekx(ksin(mx)−mcos(mx))+C.
First, rewrite a3x as e3xlna. So, k=3lna and m=2.
∫a3xsin(2x)dx=∫e3xlnasin(2x)dx
Applying the formula:
=(3lna)2+22e3xlna(3lnasin(2x)−2cos(2x))+C
Substitute e3xlna back to a3x:
=(3lna)2+4a3x(3lnasin(2x)−2cos(2x))+C
= \frac{a^{3x}{9 (\ln a)^2 + 4} (3 \ln a \sin(2x) - 2 \cos(2x)) + C}
Step 2: Solve integral 2.2.
We need to evaluate ∫cot4(2x)3dx.
Use the identity cotx1=tanx.
∫cot4(2x)3dx=∫3tan4(2x)dx
Let u=2x, so du=2dx, which means dx=21du.
=3∫tan4u(21)du=23∫tan4udu
Use the reduction formula for ∫tannudu=n−1tann−1u−∫tann−2udu.
For n=4:
∫tan4udu=3tan3u−∫tan2udu
For ∫tan2udu, use the identity tan2u=sec2u−1:
∫tan2udu=∫(sec2u−1)du=tanu−u+C1
Substitute this back:
∫tan4udu=3tan3u−(tanu−u)+C1
Now substitute this back into the main integral:
23(3tan3u−tanu+u)+C
Substitute u=2x:
=23(3tan3(2x)−tan(2x)+2x)+C
=21tan3(2x)−23tan(2x)+3x+C
= \frac{1{2} \tan^3(2x) - \frac{3}{2} \tan(2x) + 3x + C}
Step 3: Solve integral 2.3.
We need to evaluate ∫sin5(ax)cos3(ax)dx.
Since the power of cos(ax) is odd, let u=sin(ax).
Then du=acos(ax)dx, so cos(ax)dx=a1du.
Rewrite cos3(ax) as cos2(ax)cos(ax)=(1−sin2(ax))cos(ax).
∫sin5(ax)cos3(ax)dx=∫sin5(ax)(1−sin2(ax))cos(ax)dx
Substitute u=sin(ax):
=∫u5(1−u2)a1du
=a1∫(u5−u7)du
Integrate term by term:
=a1(6u6−8u8)+C
Substitute back u=sin(ax):
=a1(6sin6(ax)−8sin8(ax))+C
= \frac{\sin^6(ax){6a} - \frac{\sin^8(ax)}{8a} + C}
Step 4: Solve integral 2.4.
We need to evaluate ∫3x2−2x+91dx.
Complete the square in the denominator.