How to Learn the Types of Triangles
Triangles are classified two ways — by their sides and by their angles — and a triangle can be described by one from each group. Knowing the six names is core geometry. This deck teaches both classifications and the key facts.
There are 10 cards in the deck below. You can read through them, practise them right here with the flip-card player, and then save the deck to study properly with spaced repetition — the method that makes them stick for months, not minutes.
Why the types of triangles is hard to memorize (and the fix)
People confuse the "by sides" names (equilateral, isosceles, scalene) with the "by angles" names (right, acute, obtuse). Keeping the two systems separate is the key.
The fix is active recall plus spaced repetition. Instead of re-reading the list (which feels productive but barely works), you test yourself — pull each answer out of memory — and you review each card on a schedule that stretches over time. Every time you successfully recall a fact, the memory gets stronger and the next review is pushed further out. That's how you go from "I saw it once" to "I just know it."
The fastest way to learn the types of triangles
- Break it into small batches. Learn the three "by sides" types first, then the three "by angles" types, then combine (e.g. a right isosceles triangle).
- Test, don't re-read. Look at the question, say the answer out loud before flipping the card. The little struggle to recall is what builds the memory — a smooth re-read does almost nothing.
- Review on a schedule. Spaced repetition shows you each card right before you'd forget it. Get one right and it comes back in a few days, then a week, then a month. Miss one and it comes back sooner.
- Keep sessions short and daily. Five to ten minutes a day beats a two-hour cram every time. Consistency is the whole game.
One fact per card. The angles of any triangle always add up to 180° — the single most useful triangle fact.
The full deck: the Types of Triangles
Here's every card in the set. Practise them above, or save the deck and let spaced repetition schedule your reviews automatically.
| Question | Answer |
|---|---|
| What is an equilateral triangle? | All three sides equal and all angles 60° |
| What is an isosceles triangle? | Two sides equal (and two equal angles) |
| What is a scalene triangle? | All sides and all angles different |
| What is a right triangle? | One angle is exactly 90° |
| What is an acute triangle? | All three angles are less than 90° |
| What is an obtuse triangle? | One angle is greater than 90° |
| What do the angles of any triangle add up to? | 180° |
| What are the angles in an equilateral triangle? | All 60° |
| Can a triangle be both right and isosceles? | Yes — a right isosceles triangle (angles 90°, 45°, 45°) |
| The two ways to classify triangles are by…? | Their sides and their angles |
Save this deck and actually remember it
Create a free account, keep this 10-card deck, and we'll schedule every review at the perfect moment. First deck free forever — no credit card.
Study this deck free →FAQ: learning the types of triangles
How long does it take to learn the types of triangles?
Most people can lock in the types of triangles within one to three weeks of short daily sessions. With spaced repetition doing 10–10 cards a day, you'll recognise them within days and recall them reliably within a couple of weeks.
What's the best way to memorize the types of triangles?
Active recall plus spaced repetition. Test yourself instead of re-reading, and review on a schedule that spaces the cards out over time. Flashcards are built for exactly this — which is why the deck above is the fastest path.
Is this deck free?
Yes. You can practise all 10 cards on this page for free with no account. Sign up (also free) to save the deck and let spaced repetition schedule your reviews so it sticks long-term.