Explore the world of trigonometry by mastering right triangles and their applications, understanding and graphing trig functions, solving problems involving non-right triangles, and unlocking the power of …

Practice problem 2: right triangle What is the area of the triangle? Drag the dot to help you remember the formula.

Find the length of the hypotenuse or a leg of a right triangle using the Pythagorean theorem.

The area of a rectangle and a parallelogram is found by multiplying the base by the height. For a triangle, the area is half of a parallelogram's, so it's calculated by multiplying the base by the height …

Let's derive the formula for the area of a triangle when the coordinates of its vertices are given.

Learn eighth grade math, including geometry concepts like transformations, congruence, similarity, and the Pythagorean theorem. (aligned with Common Core standards)

Learn high school geometry—transformations, congruence, similarity, trigonometry, analytic geometry, and more (aligned with Common Core standards).

Area and perimeter help us measure the size of 2D shapes. We’ll start with the area and perimeter of rectangles. From there, we’ll tackle trickier shapes, such as triangles and circles.

Area and perimeter help us measure the size of 2D shapes. We’ll start with the area and perimeter of rectangles. From there, we’ll tackle trickier shapes, such as triangles and circles.

The area of a triangle is found by multiplying one half of the base by the height. In our example, the base is 18 and the height is 6. So, half of 18 is 9, and 9 times 6 equals 54 square units.