Rice University
Rice University: Geometry Online: Impossible Triangles
This site has an activity that displays several impossible triangles. The rules for triangles are also displayed. The student has to determine which rule has been violated for each impossible triangle.
Mangahigh
Mangahigh: Shape: Right Angle in a Semi Circle Rule
Test your knowledge of the measurement of angles in a triangle.
CK-12 Foundation
Ck 12: Geometry: Applications of the Pythagorean Theorem
[Free Registration/Login may be required to access all resource tools.] In this lesson students use the Pythagorean Theorem to find perimeter and area. Students examine guided notes, review guided practice, watch instructional videos and...
CK-12 Foundation
Ck 12: Geometry: Applications of the Pythagorean Theorem
[Free Registration/Login may be required to access all resource tools.] This concept introduces students to several applications of the Pythagorean Theorem. Students examine guided notes, review guided practice, watch instructional...
CK-12 Foundation
Ck 12: Geometry: Inverse Trigonometric Ratios
[Free Registration/Login may be required to access all resource tools.] This concept teaches students to use inverse trigonometric ratios to solve for missing angles in right triangles.
TeachEngineering
Teach Engineering: You've Got Triangles!
Students learn about trigonometry, geometry and measurements while participating in a hands-on interaction with LEGO MINDSTORMS NXT technology. First they review fundamental geometrical and trigonometric concepts. Then, they estimate the...
Khan Academy
Khan Academy: Right Triangle Trigonometry Review
Review right triangle trigonometry and how to use it to solve problems.
Oswego City School District
Regents Exam Prep Center: Pythagorean Theorem
Who was Pythagoras and what is his theorem? Explore this concept and its relationship to the measurement of a right triangle in this test prep lesson plan. The instructional activity includes an interactive worksheet where middle...
Texas Instruments
Texas Instruments: Cottage Water Problem
Students use the Cabri Geometry II Plus software to solve a geometry problem. They move the vertex point that is common to two right triangles along the base to find the smallest possible sum of the length of the hypotenuse.
CK-12 Foundation
Ck 12: Trigonometry: Pythagorean Theorem to Classify Triangles
[Free Registration/Login may be required to access all resource tools.] Use the Pythagorean Theorem to determine if triangles are acute, obtuse, or right triangles.
CK-12 Foundation
Ck 12: Converse of the Pythagorean Theorem
[Free Registration/Login may be required to access all resource tools.] Learn about the converse of the Pythagorean Theorem and some of its applications. Also explains how to identify acute and obutse triangles through the use of the...
CK-12 Foundation
Ck 12: Geometry: Sine, Cosine, Tangent
[Free Registration/Login may be required to access all resource tools.] This concept teaches students to find the sine, cosine, and tangent of right triangles.
CK-12 Foundation
Ck 12: Geometry: Sine, Cosine, Tangent
[Free Registration/Login may be required to access all resource tools.] Find the sine, cosine, and tangent of right triangles.
Mathigon
Mathigon: Geometry: Triangles and Trigonometry: Pythagoras' Theorem
Pythagoras' Theorem: In any right-angled triangle, the square of the length of the hypotenuse (the side that lies opposite the right angle) is equal to the sum of the squares of the other two sides. (A+B=C)
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.
Khan Academy
Khan Academy: Area of Triangles
Practice finding the area of right, acute, and obtuse triangles. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
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...
Texas Instruments
Texas Instruments: Walking the Fence Line, Then the Hypotenuse
In this activity, students use the Geoboard to determine the length of the hypotenuse of a right triangles. [Requires Adobe Reader.]
Other
Ic Teachers: Shapes: Triangles
Are you looking for a very basic website that will explain the basic properties of a triangle? Use this site to learn about the properties of equilateral triangles, isosceles triangles, right triangles,and scalene triangles. There are...
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.
Geometry Help
Geometry Help: Pythagorean Theorem
Explains the basic concept of the Pythagorean Theorem with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
National Council of Teachers of Mathematics
The Math Forum: Using Geoboards in the Classroom
A thorough look at the extensive uses of geoboards in the classroom. Links are listed which give introductory information on geoboards - for teachers new to using them. Then, lesson plans are provided for using geoboards in teaching...
CK-12 Foundation
Ck 12: Interactive Geometry: 17.1 Tangent Ratio
Explore and understand tangent ratios.
CK-12 Foundation
Ck 12: Geometry: Trigonometric Ratios With a Calculator Grades 9 10
[Free Registration/Login may be required to access all resource tools.] This concept teaches students to find trigonometric ratios with a calculator in order to find missing sides of right triangles.