The following lists useful trig identities. If you want to challenge yourself, try proving each of them. You can download these identities by clicking here.

**Lesson 2: Solving equations and inequalities**

- Why solve equations?
- Solving equations: Quadratics
- Exercises: Solve quadratic equations
- Solving equations: Absolute values
- Exercises: Solve equations involving absolute value
- Solving equations: Polynomials
- Exercises: Solve polynomial equations
- Solving equations: Rational expressions
- Exercises: Solve equations involving rational expressions
- Solving equations: Exponents
- Exercises: Solve exponential equations
- Solving equations: Logs
- Exercises: Solve logarithmic equations
- Solving equations: Trigonometric functions
- Trig identities 📝
- Exercises: Solve trigonometric equations
- Why solve inequalities?
- Solving inequalities
- Exercises: Solve inequalities