Logarithmic Functions

Graph and analyse logarithmic functions for IB Maths. Understand as inverses of exponentials.

y=log⁡axy = \log_a x is the inverse of y=axy = a^x. Understanding their graphs and properties is essential for IB Maths.

Key Features of $y = \log_a x$ ($a > 1$)

  • Domain: x>0x > 0. Range: all reals.
  • Passes through (1,0)(1, 0) and (a,1)(a, 1).
  • Vertical asymptote: x=0x = 0.
  • Increasing function.

Transformations

y=log⁡a(x−h)+ky = \log_a(x - h) + k: shift right hh, up kk. VA at x=hx = h.

Relationship with Exponentials

y=log⁡axy = \log_a x and y=axy = a^x are reflections in y=xy = x.

alog⁡ax=xa^{\log_a x} = x and log⁡a(ax)=x\log_a(a^x) = x.

Worked Example

f(x)=ln⁡(x−2)+1f(x) = \ln(x - 2) + 1.

Domain: x>2x > 2. VA: x=2x = 2. Passes through (3,1)(3, 1).

Practice Problems

    1. Sketch y=log⁡2(x+1)−3y = \log_2(x+1) - 3. State domain, range, and VA.
    1. Find the inverse of f(x)=ex−1+2f(x) = e^{x-1} + 2.

Want to check your answers and get step-by-step solutions?

Get it on Google PlayDownload on the App Store

Key Takeaways

  • ✓

    log⁡\log and exponential are inverses.

  • ✓

    Domain of log⁡\log: argument must be positive.

  • ✓

    VA at where the argument equals zero.

Ready to Ace Your IB maths?

Get instant step-by-step solutions to any problem. Snap a photo and learn with Tutor AI — your personal exam prep companion.

Get it on Google PlayDownload on the App Store