Newest
Acute right and obtuse angles
The difference between acute, obtuse and right angles
Khan Academy
Angle basics and measurement
554
05:31
Measuring angles
Using the KA virtual protractor to measure angles
Khan Academy
Angle basics and measurement
548
04:04
Measuring angles in degrees
How to measure an angle in degrees
Khan Academy
Angle basics and measurement
548
08:21
Angle basics
Definition of an angle. How to denote an angle using points on the angle (including the vertex)
Khan Academy
Angle basics and measurement
553
06:48
The golden ratio
An introduction to one of the most amazing ideas/numbers in mathematics
Language and notation of the circle
Formal definition of a circle. Tangent and secant lines. Diameters and radii. major and minor arcs
Lines, line segments, and rays
Difference between lines, line segments, and rays
Euclid as the father of geometry
Euclid and his Elements (and how much Abraham Lincoln liked them)
Inverse property of addition
The simple idea that a number plus its negative is 0
Khan Academy
Arithmetic properties
520
02:59
Inverse property of multiplication
Simple idea that multiplying by a numbers multiplicative inverse gets you back to one
Khan Academy
Arithmetic properties
472
03:16
