Step 1: Use integration by parts. Let u=secx and dv=sec2xdx.
Then du=secxtanxdx and v=tanx.
Step 2: Apply the integration by parts formula: ∫udv=uv−∫vdu.
∫sec3xdx=secxtanx−∫tanx(secxtanx)dx
∫sec3xdx=secxtanx−∫secxtan2xdx
Step 3: Use the identity tan2x=sec2x−1.
∫sec3xdx=secxtanx−∫secx(sec2x−1)dx
∫sec3xdx=secxtanx−∫(sec3x−secx)dx
Step 4: Distribute the integral.
∫sec3xdx=secxtanx−∫sec3xdx+∫secxdx
Step 5: Let I=∫sec3xdx. The equation becomes:
I=secxtanx−I+∫secxdx
Step 6: Add I to both sides.
2I=secxtanx+∫secxdx
Step 7: Evaluate the integral of secx.
∫secxdx=ln∣secx+tanx∣+C
Step 8: Substitute this back into the equation for 2I.
2I=secxtanx+ln∣secx+tanx∣+C
Step 9: Solve for I.
I=21(secxtanx+ln∣secx+tanx∣)+C
The final answer is 21(secxtanx+ln∣secx+tanx∣)+C.