Welch Teaching & Coaching
Trigonometry • College Preparatory Mathematics

Unit 4: Graphing Trigonometric Functions

Build sine and cosine graphs from the unit circle, then analyze transformations and graph all six trigonometric functions.

U4
Unit Road Map

Lesson Map

Use this table as your route through the unit. Lesson numbers jump directly to the matching explanation.

LessonTopicYou should be able to…
4.1From Unit Circle to SineTrack the y-coordinate as an angle rotates to create y=sin x.
4.2From Unit Circle to CosineTrack the x-coordinate as an angle rotates to create y=cos x.
4.3Amplitude, Midline & Vertical ShiftIdentify and use vertical features of sinusoidal graphs.
4.4Period & FrequencyConnect horizontal scale to repeated cycles.
4.5Phase ShiftInterpret horizontal translations of sine and cosine.
4.6Tangent & CotangentGraph periodic functions with zeros and vertical asymptotes.
4.7Secant & CosecantUse reciprocal relationships to graph secant and cosecant.
Navigation

How the Unit Is Built

Each resource below is part of the same learning cycle. Select a card to jump to it.

Learn

Content Summary

Work through these lessons in order. Focus on the meaning of the mathematics, the decision that selects a method, and a check that confirms the result.

Lesson 4.1

From Unit Circle to Sine

Track the y-coordinate as an angle rotates to create y=sin x.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Lesson 4.2

From Unit Circle to Cosine

Track the x-coordinate as an angle rotates to create y=cos x.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Lesson 4.3

Amplitude, Midline & Vertical Shift

Identify and use vertical features of sinusoidal graphs.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Lesson 4.4

Period & Frequency

Connect horizontal scale to repeated cycles.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Lesson 4.5

Phase Shift

Interpret horizontal translations of sine and cosine.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Lesson 4.6

Tangent & Cotangent

Graph periodic functions with zeros and vertical asymptotes.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Lesson 4.7

Secant & Cosecant

Use reciprocal relationships to graph secant and cosecant.

What to understand: Explain what the method is doing, not only which buttons or steps produce an answer.
Check: Ask whether the sign, size, units, quadrant, restrictions, or graph behavior make sense before accepting the result.
Watch & Reinforce

Video Library

These links open focused video searches by lesson topic. Use them as reinforcement rather than as a substitute for showing your own reasoning.

Lesson 4.1

From Unit Circle to Sine

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Lesson 4.2

From Unit Circle to Cosine

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Lesson 4.3

Amplitude, Midline & Vertical Shift

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Lesson 4.4

Period & Frequency

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Lesson 4.5

Phase Shift

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Lesson 4.6

Tangent & Cotangent

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Lesson 4.7

Secant & Cosecant

Use a short lesson after reading the website explanation, then return to the practice.

Find a matching video →
Language

Vocabulary

These terms should appear naturally in explanations, diagrams, and written reasoning.

amplitude
Write a definition in your own words and add an example or sketch in your STRIDES notes.
period
Write a definition in your own words and add an example or sketch in your STRIDES notes.
frequency
Write a definition in your own words and add an example or sketch in your STRIDES notes.
midline
Write a definition in your own words and add an example or sketch in your STRIDES notes.
phase shift
Write a definition in your own words and add an example or sketch in your STRIDES notes.
vertical shift
Write a definition in your own words and add an example or sketch in your STRIDES notes.
asymptote
Write a definition in your own words and add an example or sketch in your STRIDES notes.
sinusoid
Write a definition in your own words and add an example or sketch in your STRIDES notes.
secant
Write a definition in your own words and add an example or sketch in your STRIDES notes.
cosecant
Write a definition in your own words and add an example or sketch in your STRIDES notes.
cotangent
Write a definition in your own words and add an example or sketch in your STRIDES notes.
Practice

Sample Problems

Try each problem before opening the solution. The examples are original practice aligned to the unit skills.

1

Read a sinusoid

For y=3sin x−2, state amplitude and midline.
Show solution
Amplitude=3; midline y=−2.
2

Period

Find the period of y=cos(2x).
Show solution
2π/2=π.
3

Phase shift

State the phase shift of y=sin(x−π/4).
Show solution
Right π/4.
4

Build a model

A sinusoid has max 9 and min 3. Find amplitude and midline.
Show solution
Amplitude=(9−3)/2=3; midline=(9+3)/2=6.
5

Tangent

Find the period of y=tan(3x).
Show solution
π/3.
6

Reciprocal graph

Explain where y=sec x has vertical asymptotes.
Show solution
Where cos x=0: x=π/2+kπ.
Reference

Equations & Rules

Know what each relationship means and when it applies; do not treat the box as a list of disconnected formulas.

Sinusoid Form
y = A sin(B(x−C))+D or y = A cos(B(x−C))+D
Amplitude
|A|
Midline
y = D
Sine/Cosine Period
2π/|B|
Tangent/Cotangent Period
π/|B|
Phase Shift
C in A trig(B(x−C))+D
Reciprocal Graphs
sec x=1/cos x; csc x=1/sin x
Prepare

Review Guide

Skill Checklist

  • I can track the y-coordinate as an angle rotates to create y=sin x.
  • I can track the x-coordinate as an angle rotates to create y=cos x.
  • I can identify and use vertical features of sinusoidal graphs.
  • I can connect horizontal scale to repeated cycles.
  • I can interpret horizontal translations of sine and cosine.
  • I can graph periodic functions with zeros and vertical asymptotes.
  • I can use reciprocal relationships to graph secant and cosecant.

How to review

  1. Complete the unit Skills Check packet without notes.
  2. Mark the exact skill behind each error.
  3. Return to that lesson and complete a fresh example.
  4. Explain the correction in words, then retry a similar problem.
  5. Finish with mixed practice so you must choose the method yourself.
Apply

Performance Task

Periodic Data Model

Collect or use periodic data such as daylight, tides, seasonal temperature, Ferris-wheel height, or a rotating sensor. Build a sinusoidal model and interpret amplitude, midline, period, and phase shift in context.

Evidence to include

A labeled mathematical model, organized calculations, appropriate units and precision, a written interpretation, and a check or discussion of limitations.