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Triangle Worksheets

Triangle worksheets contain recognizing and identifying triangles based on sides and angles; finding interior and exterior angles; simple algebra problems; area and perimeter of triangle; finding area for special triangles such as equilateral, isosceles and scalene; advanced topics such as triangle inequality theorem, largest and smallest angle, shortest and longest side and finding centroid.

For basic triangle recognition practice and charts, please refer 2D Shapes Worksheets

Classifying Triangles

Identifying Triangles Based on Sides

Label each triangle. Based on sides, you can classify triangle as equilateral, isosceles and scalene. Use ruler wherever necessary.

Triangle classification based on sides

No Measures: Sheet 1 | Sheet 2 | Sheet 3

Measures in Numerals: Sheet 1 | Sheet 2 | Sheet 3

Measures in Variables: Sheet 1 | Sheet 2 | Sheet 3

Identifying Triangles Based on Angles

Label each triangle. Based on angles, you can classify triangle as acute, obtuse and right.

Triangle classification based on angles

Sheet 1 | Sheet 2 | Sheet 3

Identifying Triangles: Both Sides and Angles

Classify each triangle by considering the measures of both sides and angles.

Identifying types of triangles

No Measures: Sheet 1 | Sheet 2 | Sheet 3

Measures in Numerals: Sheet 1 | Sheet 2 | Sheet 3

Measures in Variables: Sheet 1 | Sheet 2 | Sheet 3

Classifying Triangles: Select all that apply

There are types of triangles along the row and different triangle images along the column. Tick the boxes that apply to each triangle.

Classifying Triangles

No Measures: Sheet 1 | Sheet 2 | Sheet 3

Measures in Numerals: Sheet 1 | Sheet 2 | Sheet 3

Measures in Variables: Sheet 1 | Sheet 2 | Sheet 3

Angles in Triangle

Finding Interior Angle

Apply angle sum theorem to find the unknown interior angle in each triangle.

Interior Angles

Interior 1 | Interior 2 | Interior 3

Finding Exterior Angle

Applying exterior angle theorem, find the measure of an exterior angle in each triangle.

Finding exterior angle

Exterior 1 | Exterior 2 | Exterior 3

Algebra in Triangles

Identifying Unknown Interior Angle

Find the value of x. Using x value, find the measure of unknown interior angle.

Missing interior angles

Easy: Sheet 1 | Sheet 2 | Sheet 3

Medium: Sheet 1 | Sheet 2 | Sheet 3

Identifying Unknown Exterior Angle

Set the equation applying exterior angle theorem and find the value of x. Also find the missing exterior angle.

Missing exterior angles

Easy: Sheet 1 | Sheet 2 | Sheet 3

Medium: Sheet 1 | Sheet 2 | Sheet 3

Finding length of the Sides

With the perimeter and algebraic expressions, set the equation and find the value of x. By applying the value of x, compute the length of all the sides of a triangle.

Missing sides

Sheet 1 | Sheet 2 | Sheet 3

Area and Perimeter of Triangle

Perimeter of Triangle: Standard

Add up the lengths of all the sides and find the perimeter of a triangle.

Finding perimeter

Sheet 1 | Sheet 2 | Sheet 3

Perimeter of Triangle: Congruent Properties

Find the perimeter with the given measures and congruent sides.

Perimeter with congruent sides

Sheet 1 | Sheet 2 | Sheet 3

Area of Triangle: Base and Height

Using the formula A = 1/2 * base * height, find the area of each triangle. Challenging worksheet requires unit conversion.

Finding area

Easy: Sheet 1 | Sheet 2 | Sheet 3

Medium: Sheet 1 | Sheet 2 | Sheet 3

Hard: Sheet 1 | Sheet 2 | Sheet 3

Challenging: Sheet 1 | Sheet 2 | Sheet 3

Area of an Equilateral Triangle

Use the formula A = sqrt(3)/4 * a2, where 'a' refers to length of the side. Each worksheet has 9 problems finding area of an equilateral triangle.

Area of equilateral triangle

Sheet 1 | Sheet 2 | Sheet 3

Area of an Isosceles Triangle

Find the height using Pythagorean theorem, and then apply the standard formula to find the area of each isosceles triangle.

Area of an Isosceles Triangle

Sheet 1 | Sheet 2 | Sheet 3

Area of Scalene Triangle

Apply Heron's formula (also called Hero's formula) to find the area of each scalene triangle. Round the answer to 2 decimal places.

Area of Scalene Triangle

Sheet 1 | Sheet 2 | Sheet 3

Missing base or height

To find the base, B = 2A / H. To find the height, H = 2A / B. Applying this technique, find the missing side for each triangle.

Missing base or height

Sheet 1 | Sheet 2 | Sheet 3

Advanced Triangle Worksheets

Relation between Sides and Angles

Each worksheet has 2 sections. In first section, find the largest and smallest angle with known sides. In second section, find the longest and smallest side for each triangle with known angles.

Relation between angles and sides

Sheet 1 | Sheet 2 | Sheet 3

Triangle Inequality Theorem

Apply triangle inequality theorem and identify whether the triangle is possible or not possible with the given sides.

Triangle inequality theorem

Sheet 1 | Sheet 2 | Sheet 3

Finding Centroid

Each worksheet has 9 problems finding centroid of each triangle with coordinates at vertices.

Finding Centroid

Sheet 1 | Sheet 2 | Sheet 3