Students will see how the difference formula for tan can be used to find the acute angle between two lines, firstly, when neither line is vertical, then when exactly one line is vertical.
Watch these Eddie Woo videos:
Conclude by giving your students these challenges:
- What Is the Time? by NRICH
- Blue and White by NRICH
- Mini-max by NRICH
- 2007 AMC 8, Problem 12