Browse lessons
Algebra
Geometry
Trigonometry
Algebra II
Calculus
Statistics
Learn about functions, graphs, lines, and polynomials. "Algebra" is the math for describing how different things are related.
SUBJECT
COMPLETION

COMPLETION

Log in to track progress
Addition and subtraction
Multiplication and division


Multiplying by 1 and 0
Discover what happens when you multiply by 1 and 0

![]() | Start lesson |
![]() | Log in to review |


Order of operations
Is there more than one way to evaluate an expression?

![]() | Start lesson |
![]() | Log in to review |
Factoring


Factoring out negatives
Flip the signs when you factor out negative numbers

![]() | Start lesson |
![]() | Log in to review |
Fractions


Multiplying fractions
What's 1/2 times 3/5? Learn the trick in this lesson!

![]() | Start lesson |
![]() | Log in to review |


Comparing fractions
How to tell when fractions are equal or which is bigger

![]() | Start lesson |
![]() | Log in to review |


Dividing fractions
Dividing by a fraction is really multiplying by its reciprocal!

![]() | Start lesson |
![]() | Log in to review |


Distributing division
The distributive law works for multiplying, but also dividing

![]() | Start lesson |
![]() | Log in to review |


When 'of' means multiply
Evaluating fractions of numbers (like 5/7 of 210)

![]() | Start lesson |
![]() | Log in to review |
Powers and roots


Roots of non-squares
How to find the roots of numbers that are NOT square

![]() | Start lesson |
![]() | Log in to review |


Cube roots and beyond
Cube roots, fourth roots, fifth roots, and so on...

![]() | Start lesson |
![]() | Log in to review |
Rules for powers


Distributing powers
It works for multiplication and division, but that's it!

![]() | Start lesson |
![]() | Log in to review |
Solving equations


Solving by multiplying
Multiplying or dividing on both sides of equations

![]() | Start lesson |
![]() | Log in to review |


Multivariable equations
Solving equations when they have more than one variable

![]() | Start lesson |
![]() | Log in to review |


Unsolvable equations
Some equations have no solutions, others have plenty!

![]() | Start lesson |
![]() | Log in to review |
Inequalities and simultaneous equations


2 equations, 2 unknowns
Solve for both variables when you have two equations

![]() | Start lesson |
![]() | Log in to review |


2 equations, no solution
Sometimes two equations have no solutions, or many!

![]() | Start lesson |
![]() | Log in to review |
Coordinates


Finding a midpoint
Given two points, which point is exactly halfway between?

![]() | Start lesson |
![]() | Log in to review |
Slope


Find the slope of any line
Two steps that will always give you the correct slope

![]() | Start lesson |
![]() | Log in to review |
Lines


Solving for intersections
Given two lines, can you determine where they cross?

![]() | Start lesson |
![]() | Log in to review |


Inequalities (2 variables)
Simplify inequalities with two variables and test solutions

![]() | Start lesson |
![]() | Log in to review |
Polynomials
Quadratics


Factoring quadratics
An extremely useful trick for solving some equations

![]() | Start lesson |
![]() | Log in to review |


Discriminants and roots
A quick way to tell how many solutions a quadratic has

![]() | Start lesson |
![]() | Log in to review |
The mathematics of lines, shapes, and angles. Essential stuff for describing the world around you.
SUBJECT
COMPLETION

COMPLETION

Log in to track progress
Lines and angles
Related angles


Corresponding angles
Parallel lines form congruent angles in matching places

![]() | Start lesson |
![]() | Log in to review |
Triangles


Isosceles triangles
They have two equal sides, but what about their angles?

![]() | Start lesson |
![]() | Log in to review |


Big angles, longer sides
In triangles, sides and their opposite angles are related!

![]() | Start lesson |
![]() | Log in to review |
Triangle congruence and similarity


AA Postulate (Similarity)
Triangles are similar when they have matching angles

![]() | Start lesson |
![]() | Log in to review |


SSA (ambiguous case)
Depending on the sides, you can have 0, 1, or 2 triangles!

![]() | Start lesson |
![]() | Log in to review |
Polygons and quadrilaterals


Angles in polygons
Find a formula for the sum of the angles in any polygon

![]() | Start lesson |
![]() | Log in to review |


Paralleogram diagonals
In parallelograms, diagonals always bisect each other

![]() | Start lesson |
![]() | Log in to review |
Area of polygons
The Pythagorean theorem


Proving Heron's formula
You might know the formula, but where does it come from?

![]() | Start lesson |
![]() | Reviews coming soon |
Circles, ellipses, and their areas


Circumference and Pi
Find the distance around a circle (and then eat some pi)

![]() | Start lesson |
![]() | Log in to review |
Angles in circles


Central angles and arcs
As you'll see, there are 360 degrees in every circle

![]() | Start lesson |
![]() | Log in to review |


Inscribed angles
Discover how inscribed angles are related to central angles!

![]() | Start lesson |
![]() | Log in to review |


Inscribing the diameter
Prove that inscribed angles drawn to diameters are right

![]() | Start lesson |
![]() | Log in to review |
Lines in circles


Secant and tangent lines
Some lines cross circles twice, others touch them only once

![]() | Start lesson |
![]() | Log in to review |


Circumscribed angles
Discover how angles between tangents are related to arcs

![]() | Start lesson |
![]() | Log in to review |
Volume


Cavalieri's Principle (3D)
Instead of matching widths, you'll be matching areas!

![]() | Start lesson |
![]() | Log in to review |
Surface area


Pyramid surface area
Find a pyramid's surface area using squares and triangles

![]() | Start lesson |
![]() | Log in to review |


Cone surface area
Discover and use the formula for a cone's surface area!

![]() | Start lesson |
![]() | Log in to review |


Internal diagonals
What's the distance between opposite corners of a cube?

![]() | Start lesson |
![]() | Log in to review |
Transformations
Geometric optics


Rainbows explained
Use refraction to understand rainbows and their features

![]() | Start lesson |
![]() | Reviews coming soon |
Trigonometry helps you understand any topic that involves distances, angles, or waves. The trig functions (sin, cos, and tan) show up all over science and engineering.
SUBJECT
COMPLETION

COMPLETION

Log in to track progress
Radians


Radians and degrees
How to switch back and forth between units for angles

![]() | Start lesson |
![]() | Reviews coming soon |


Lengths of circular arcs
A formula for arc length in terms of radius and angle

![]() | Start lesson |
![]() | Reviews coming soon |
Trig functions


Sides of right triangles
Your friendly hypotenuses, opposites, and adjacents

![]() | Start lesson |
![]() | Reviews coming soon |


Components (and cops)
Find legs of right triangles, and don't get pulled over!

![]() | Start lesson |
![]() | Reviews coming soon |
Special angles


30/60 degrees
Calculate the sine, cosine, and tangent of 30 and 60 degrees

![]() | Start lesson |
![]() | Log in to review |


0/90 degrees
Calculate the sine, cosine, and tangent of 0 and 90 degrees

![]() | Start lesson |
![]() | Reviews coming soon |
The unit circle


Trig for larger angles
What's sin(250)? Use the unit circle to tackle bigger angles

![]() | Start lesson |
![]() | Reviews coming soon |


Trig for negative angles
Using the unit circle for trig with negative angles

![]() | Start lesson |
![]() | Reviews coming soon |


Trig for coterminals
How trig functions are related for coterminal angles

![]() | Start lesson |
![]() | Reviews coming soon |
Inverse trig functions
Trig identities
Triangle formulas


Triangulation
Real-world application of the law of sines to find distances

![]() | Start lesson |
![]() | Reviews coming soon |


Triangle area: SAS
Find a triangle's area using 2 sides and the angle between

![]() | Start lesson |
![]() | Reviews coming soon |
Take the next step in Algebra! Here we'll introduce the most common functions you're likely to see, and different ways to describe functions.
SUBJECT
COMPLETION

COMPLETION

Log in to track progress
Real numbers
Imaginary and complex numbers


Working with imaginaries
Add, subtract, multiply, and divide imaginary numbers

![]() | Start lesson |
![]() | Log in to review |
Functions


Describing functions
Make your own functions, and live to tell the tale

![]() | Start lesson |
![]() | Reviews coming soon |


Odd and even functions
Turns out functions can be "odd" and "even" too

![]() | Start lesson |
![]() | Reviews coming soon |
Exponents
Logarithms
Playing with functions
Conic sections
Rational functions
Polar functions
The mathematics of change. And it'll use just about every branch of math you've learned before it.
SUBJECT
COMPLETION

COMPLETION

Log in to track progress
Limits


Limits to infinity
What happens to functions as x gets really, really big?

![]() | Start lesson |
![]() | Reviews coming soon |


Continuity (for real)
Dive deeper into continuity, using one-sided limits

![]() | Start lesson |
![]() | Reviews coming soon |


Splitting limits
Tricks for simplifying limits (and when they don't work!)

![]() | Start lesson |
![]() | Reviews coming soon |
Derivatives
Integrals
Series
The math of data collection and analysis. Very useful for finding trends and making predictions!
SUBJECT
COMPLETION

COMPLETION

Log in to track progress
Sensitivity analysis


Sensitivity and specificity
Quantifying whether tests for diseases are any good

![]() | Start lesson |
![]() | Log in to review |


Cutoffs and ROCs
Sensitivity vs. specifity, cutoff selection, and ROC curves

![]() | Start lesson |
![]() | Log in to review |
Distributions
Regression analysis
Hypothesis testing