Maths lessons

“Maths Spelled Out” is a free online maths textbook for secondary school, sixth form and university. We explain everything step by step in plain words, with pictures and worked examples. You’ll find the articles sorted by topic in the menu on the left.

Most read articles

• Trigonometric functions: sine, cosine, tangent and cotangent.
• Trigonometric identities: the formulas you need for trigonometric functions.
• Probability: how likely something is to happen, and how to calculate it.
• Fractions: adding, subtracting, multiplying and dividing fractions.
• Logarithmic functions: what a logarithm is and what its graph looks like.
• Sequences: what a sequence is and what properties it can have.
• Derivatives: what a derivative means and how to find it.
• Domain of a function: for which values of x a function is defined.
• Properties of functions: increasing, decreasing, bounded, one-to-one and more.
• Even and odd functions: functions symmetric about the y-axis or the origin.

About this site

The site is written by Lukáš Havrlant.