# The Law of Cosines

This lesson introduces, proves, and provides examples of the law of cosines.

# Proof: Shortcut Method of Squaring a Two Digit Number

This video explains how to square any two digit number without using a calculator and shows the proof.

# Derive the Area of a Circle by Integrating the Circumference

This video explains how to derive the area formula for a circle using integration.

# Derive the Area of a Circle Using Integration (x^2+y^2=r^2)

This video explains how to derive the area formula for a circle using integration.

# Curious Calculation: 3 Digit Num Divided by Sum of Digits (Proof Included)

This video show a calculation starting with a 3 digit number with all the same digit divided by the sum of the digits is always the same result.

# Curious Calculation: Result is Always 8 (Proof Included)

This video show a calculation starting with any counting number that always results in 8. A proof is included.

# Curious Calculation: Result is Always 3 (Proof Included)

This video show a calculation starting with any counting number that always results in 3. A proof is included.