ELIAS, let's knock this out.
Step 1: Use the trigonometric identity tan2x=sec2x−1 to rewrite the integrand.
∫tan2xsecxdx=∫(sec2x−1)secxdx
Step 2: Distribute secx and split the integral into two parts.
∫(sec3x−secx)dx=∫sec3xdx−∫secxdx
Step 3: Evaluate the integral of secx.
∫secxdx=ln∣secx+tanx∣
Step 4: Evaluate the integral of sec3x using integration by parts.
Let I=∫sec3xdx.
We use integration by parts: ∫udv=uv−∫vdu.
Let u=secx and dv=sec2xdx.
Then du=secxtanxdx and v=tanx.
I=secxtanx−∫tanx(secxtanx)dx
I=secxtanx−∫secxtan2xdx
Substitute tan2x=sec2x−1 again:
I=secxtanx−∫secx(sec2x−1)dx
I=secxtanx−∫(sec3x−secx)dx
I=secxtanx−∫sec3xdx+∫secxdx
I=secxtanx−I+ln∣secx+tanx∣
Now, solve for I:
2I=secxtanx+ln∣secx+tanx∣
I=21secxtanx+21ln∣secx+tanx∣
Step 5: Combine the results from Step 3 and Step 4.
Substitute the expressions for ∫sec3xdx and ∫secxdx back into the equation from Step 2:
∫sec3xdx−∫secxdx=(21secxtanx+21ln∣secx+tanx∣)−(ln∣secx+tanx∣)+C
Step 6: Simplify the expression.
21secxtanx+21ln∣secx+tanx∣−ln∣secx+tanx∣+C
21secxtanx−21ln∣secx+tanx∣+C
The final answer is 21secxtanx−21ln∣secx+tanx∣+C.
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