Two equal sides force the two angles opposite them to be equal, and that runs both ways. In an equilateral triangle everything is equal, so every angle is 60.
Not quite the one you need? Same words, different skill:
Assuming the vertex angle is one of the equal pair. The equal angles are the ones facing the equal sides, which are the base angles, and the odd one out is at the top.
Also called base angles theorem, equilateral triangle angles or isosceles triangle.
What you can put on this worksheet
Angles in isosceles and equilateral triangles
Each base angle of an isosceles triangle is twice as large as the vertex angle. Find the measure of a base angle.→ 72∘
Side lengths: equal legs, equilateral sides, perimeter, the altitude
An isosceles triangle has a perimeter of 64 and a base of 14. Find the length of each leg.→ 25
Two isosceles triangles meeting at a crossing
Two segments cross to make two isosceles triangles, each with its equal sides at the crossing. Find x.— two triangles meeting where two segments cross, labeled 60°→ 14
Questions about these worksheets
Yes. Every isosceles and equilateral triangles sheet is free to print and free to download as a PDF. There is no account to make, no email to hand over and no limit on how many you take.
Yes. The answer key prints on a second page, and you can choose whether it shows each question beside its answer or just the answers in a list.
Yes. Print straight from the page, or download the PDF and print that. The sheet is laid out for paper rather than squeezed off a screen, so there is room to work under each question, and the answer key comes out on its own page.
Geometry is usually taken around 9th or 10th grade, though schools vary and plenty of students meet it earlier or later. Pick the difficulty rather than the grade: the easy level suits a first lesson on it, the hard level suits review before a test.
Yes, as many as you like. The questions are built fresh each time rather than picked from a fixed set of files, so pressing Generate gives a new sheet. That is what you want for a second class, a retake, or two students sitting next to each other.
That is the closest comparison, and Kuta Software is good software. It is also paid software you install on a computer. These worksheets run in a browser tab for free, with no account and nothing to install. Like Kuta, the isosceles and equilateral triangles questions are generated when you ask for them rather than pulled from a fixed set of files, so two classes never get the same sheet, and the answer key comes with it.
Yes. There are three levels, and you can tick more than one for a sheet that mixes them, in which case the questions come out easiest first. The harder levels are not just larger numbers: they ask for something the easy ones do not.
You pick from 3: angles in isosceles and equilateral triangles, side lengths: equal legs, equilateral sides, perimeter, the altitude and two isosceles triangles meeting at a crossing. Tick as many as you want and set how many of each, or let it spread them evenly.
Assuming the vertex angle is one of the equal pair. The equal angles are the ones facing the equal sides, which are the base angles, and the odd one out is at the top.