Use a triangle area formula that works when the height is unknown. The eighth installment in a 16-part series on trigonometry revisits the trigonometric triangle area formula that previously was shown to work with the acute triangles....

Transform pupils into mathematicians as they create their own definitions and formulas. Scholars examine an assortment of triangles and create a definition and formula for determining the sharpness of the vertex angle. The groups of...

Rewrite a quadratic function to easily see the transformations involved. The instructional task takes a general quadratic function and rewrites it into a form that shows the translations and scaling of the parent quadratic function. The...

Find the area as it slides. Pupils derive an equation to find the painted area of a section of a trapezoidal-shaped stage The section depends upon the sliding distance the edge of the painted section is from a vertex of the trapezoid....

The problem seems simple: find the area of the equilateral triangle whose sides are each length 1. In fact, this same problem is solved in 8th grade, addressing a different Common Core standard, using the formula for area of a triangle...

Learners rewrite a general quadratic function by completing the square to see a new form of the function that more easily identifies the x-coordinate of the vertex and the two roots of the function.

This is an interesting geometry problem. Given the figure, find the area of a triangle that is created by the intersecting lines. The solution requires one to use what he/she knows about coordinate geometry, as well as triangle...

Create a linear equation for a problem when the intercept information is not given. The two-day lesson introduces the class to the point-slope form, which can be used for problems when the initial conditions are not provided. Pupils...

A quadrilateral is drawn on the coordinate plane, and eighth grade geometers find the length of each side and the diagonals by applying the Pythagorean theorem. 

Wait, let's start over — teach your class how to return to the beginning. The first lesson plan looking at inverse matrices introduces the concept of being able to undo a matrix transformation. Learners work with matrices with a...

By first starting with an explicit example of a radius and center point, this challenging lesson tries to help students gain an understanding of the Pythagorean theorem and the equation of a circle. Once they have accomplished the first...

Have learners graph complex numbers to gain a visual and mathematical understanding of the distance and the midpoint between two complex numbers. This lesson is short, but to the point, and addresses an important complex number...

Geometric volume calculations are brought into the real world in a quick set of application problems. Learners are asked to help a patient figure out how to drink a prescribed amount of water both at work and at home. This activity...