Maths Challenge
Maths challenge.net: Triangle in a Square
A "three star" geometry problem requiring some prior knowledge in math and proofs to maximize the area of an inscribed triangle in terms of the hypotenuse.
Maths Challenge
Maths challenge.net: Shaded Triangle
A great geometry problem of area, encorperating many learned skills.
Maths Challenge
Maths challenge.net: Maximum Square
A challenging proof like geometry of finding the square inscribed in a triangle.
Maths Challenge
Maths challenge.net: Right Angle Reasoning
A geometry problem for students to use their mathematical reasoning skills to explain a right triangle property.
Maths Challenge
Maths challenge.net: Measuring Mountains
Use your triangle solving skills to solve this triangle problem and then apply it to the real world.
Maths Challenge
Maths challenge.net: Leaning Ladders
Use your right triangle solving skills to solve this ladders in a hole problem.
Maths Challenge
Maths challenge.net: Perpendicular Construction
This is a "three star" geometry problem where prior math problem skills and proof experience is recommended to solve this "Perpendicular Construction" problem.
Maths Challenge
Maths challenge.net: Tri Angles
A geometry proof involving exterior angles of a triangle.
Cuemath
Cuemath: 30 60 90 Triangle
In this lesson, learn all about the 30-60-90 triangle. Learn about its sides, its area, and the rules that apply to these triangles. Includes simulations and practice questions.
CK-12 Foundation
Ck 12: Geometry: Inscribed Similar Triangles
[Free Registration/Login may be required to access all resource tools.] Apply the fact that the altitude of a right triangle creates similar triangles.
Other
Antonio Gutierrez: Geometry From the Land of the Incas
Discovering the properties of constructions, seeing proofs in action, and viewing problems come to life here with this wonderful use of technology in the classroom. Single steps are explained and illustrated one at a time so that the...
Mangahigh
Mangahigh: Shape: Proof of the Sum of the Angles in a Triangle
Determine that all angles in a triangle equal 180 degrees.
Alabama Learning Exchange
Alex: The Pythagorean Theorem in the Real World
The introduction of this lesson has students verifying the famous Pythagorean Theorem with a hands-on proof. Students will then apply the Theorem in one of two ways: by solving for the side lengths of a right triangle and by determining...
Science Buddies
Science Buddies: Circumscribing a Circle About a Triangle
Here is a project that combines Computer Science and Mathematics. Prove a method for circumscribing a circle about a triangle (as shown). You'll also learn how to create an interactive diagram to illustrate your proof, using an applet...
Science Buddies
Science Buddies: Tangent Circles and Triangles
Here is a project that combines Computer Science and Mathematics. The two circles are tangent to one another at point A. Their diameters are parallel. Prove that points A, D and F are co-linear. You'll also learn how to create an...
Science Buddies
Science Buddies: Circles, Tangent Lines and Triangles
Here is a project that combines Computer Science and Mathematics. The semicircle has two tangent lines that meet at point T. You need to prove that a line drawn from A to T bisects CD. You'll also learn how to create an interactive...
Maths Challenge
Maths challenge.net: Corner Circle
This is a "three star" geometry problem where prior knowledge of circles and triangles is recommended to solve this circle in the corner problem.
Maths Challenge
Maths challenge.net: Shaded Hexagon
A problem with equilateral triangles and area to solve this "Shaded Hexagon" problem. Mathematical reasoning and triangle knowledge will be needed to solve the problem.
Maths Challenge
Maths challenge.net: Shaded Square
A problem of finding the fraction of a square that is shaded given criterion. Students will have to use their mathematical reasoning and triangle solving skills to solve this area problem.
Cuemath
Cuemath: Hypotenuse Leg Theorem
Explore the world of the hypotenuse leg theorem in this mini-lesson. Provides a definition, examples, and practice questions with answers that help with understanding their properties.
CK-12 Foundation
Ck 12: Geometry: Pythagorean Theorem and Pythagorean Triples
[Free Registration/Login may be required to access all resource tools.] Apply the Pythagorean Theorem and its converse. Includes videos, exercises, links to interactive activities, etc.
Sophia Learning
Sophia: Cpctc: Lesson 2
This lesson will demonstrate the use of CPCTC in triangle congruencey proofs. It is 2 of 4 in the series titled "CPCTC."