Precalc
Section 6.2

Graphs of Other Trig Functions

These graphs show up on Exam 3, usually as a 'find the period and asymptotes' question. Understanding asymptotes also helps in Section 7.5 when you're solving equations involving tangent β€” you need to know where the function exists and where it doesn't.

⚑ Quick Summary

While sine and cosine make smooth, gentle waves, the other four trig functions have a wilder personality β€” they shoot off toward infinity at certain points. These "blow-up" points are called vertical asymptotes, and they're invisible walls the graph can never cross. Tangent and secant blow up wherever cosine is zero; cotangent and cosecant blow up wherever sine is zero.

Period of Tangent / Cotangent
Period=Ο€βˆ£B∣\text{Period} = \frac{\pi}{|B|}

Half the period of sine and cosine for the same B value

Period of Secant / Cosecant
Period=2Ο€βˆ£B∣\text{Period} = \frac{2\pi}{|B|}

Same period formula as sine and cosine

πŸ“‹ Before You Start

Tap any item if you need a refresher:

Plain-English version

While sine and cosine make smooth, gentle waves, the other four trig functions have a wilder personality β€” they shoot off toward infinity at certain points. These "blow-up" points are called vertical asymptotes, and they're invisible walls the graph can never cross. Tangent and secant blow up wherever cosine is zero; cotangent and cosecant blow up wherever sine is zero.

The biggest thing to remember is the period difference. Tangent and cotangent are "impatient" β€” they repeat every Ο€βˆ£B∣\frac{\pi}{|B|} instead of the usual 2Ο€βˆ£B∣\frac{2\pi}{|B|}. That means their pattern is twice as fast as sine and cosine. Secant and cosecant keep the same 2Ο€βˆ£B∣\frac{2\pi}{|B|} period as the sine/cosine waves they're built from.

Tangent rises from βˆ’βˆž-\infty to +∞+\infty between each pair of asymptotes β€” it always goes uphill. Cotangent does the opposite β€” it always goes downhill. Secant and cosecant form U-shaped branches that open up and down, hugging the peaks and valleys of cosine and sine respectively.

When graphing a transformed version like y=Atan⁑(Bxβˆ’C)+Dy = A\tan(Bx - C) + D, the same A-B-C-D ideas from sine and cosine apply β€” just swap in the correct period formula. The most important step is finding where the asymptotes land, because they determine where each branch starts and ends. If there's a phase shift, the asymptotes shift too.

Interactive Diagram

Key Formulas

Period of Tangent / Cotangent
Period=Ο€βˆ£B∣\text{Period} = \frac{\pi}{|B|}

Half the period of sine and cosine for the same B value

Period of Secant / Cosecant
Period=2Ο€βˆ£B∣\text{Period} = \frac{2\pi}{|B|}

Same period formula as sine and cosine

Tangent Asymptotes (standard)
x=Ο€2+nΟ€,n∈Zx = \frac{\pi}{2} + n\pi, \quad n \in \mathbb{Z}

Where cos(x) = 0

Cotangent Asymptotes (standard)
x=nΟ€,n∈Zx = n\pi, \quad n \in \mathbb{Z}

Where sin(x) = 0

General Tangent Form
y=Atan⁑(Bxβˆ’C)+Dy = A\tan(Bx - C) + D

Phase shift = C/B, vertical stretch = |A|, vertical shift = D

Key Takeaways

  • βœ“Tangent/cotangent period: Ο€βˆ£B∣\frac{\pi}{|B|}; secant/cosecant period: 2Ο€βˆ£B∣\frac{2\pi}{|B|} β€” don't mix them up
  • βœ“Asymptotes come from zeros in the denominator: tan/sec blow up where cos⁑=0\cos = 0; cot/csc blow up where sin⁑=0\sin = 0
  • βœ“Tangent increases through each branch; cotangent decreases β€” they go in opposite directions
  • βœ“Phase shifts move the asymptotes too β€” set the transformed argument equal to the base asymptote values

⚠️ Common Mistakes

  • βœ—Using the sine/cosine period formula 2Ο€βˆ£B∣\frac{2\pi}{|B|} for tangent or cotangent β€” tan and cot use Ο€βˆ£B∣\frac{\pi}{|B|} instead
  • βœ—Forgetting that asymptotes shift when there's a phase shift β€” set the full transformed argument equal to the base asymptote values
  • βœ—Confusing the direction of tangent vs. cotangent β€” tangent increases through each branch, cotangent decreases
  • βœ—Forgetting that sec⁑(x)\sec(x) and csc⁑(x)\csc(x) never take values between βˆ’1-1 and 11 β€” the range always has a gap in the middle