Wolfram Research
Wolfram Math World: Acute Triangle
This MathWorld site gives a short discussion on acute triangles with links to related terms and topics. The site offers a discussion on the least number of acute triangles to compose various polygons, and a discussion on the relationship...
Illustrative Mathematics
Illustrative Mathematics: G Srt Sine and Cosine of Complementary Angles
The goal of this task is to provide a geometric explanation for the relationship between the sine and cosine of acute angles. In addition, students will need to think about the sine and cosine as functions of an angle in order to reason...
Illustrative Mathematics
Illustrative Mathematics: F Tf Trigonometric Ratios and the Pythagorean Theorem
The purpose of this task is to use the Pythagorean Theorem to establish a fundamental trigonometric identity for an acute angle. The reasoning behind this identity is then applied to calculate a cosine for a given obtuse angle. Aligns...
Illustrative Mathematics
Illustrative Mathematics: G Srt Defining Trigonometric Ratios
The purpose of this task is to use the notion of similarity to define the sine and cosine of an acute angle. Aligns with G-SRT.C.6.
Khan Academy
Khan Academy: Trigonometric Ratios in Right Triangles
Given the side lengths of a right triangle, find the sine, cosine, or tangent of one of the acute angles. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Windstream
Ojk's Precalculus Study Page: The Law of Cosines
An introduction to solving acute and obtuse triangles by using the law of cosines, including a derivation of the formula. Includes several pistures and examples.
University of Saskatchewan (Canada)
University of Saskatchewan: Trigonometric Functions
This site examines the six trigonometric functions from a right triangle point of view. Provides information, examples, and lots of exercises for understanding.
Texas Instruments
Texas Instruments: What's the Trig?
Students will be introduced to right triangle trigonometry. They will use the TI-89 and Geometer's Sketchpad to construct a right triangle and calculate sin, cosine, and tangent of various acute angles.
Math Open Reference
Math Open Reference: Triangles
A complete reference guide to types of triangles and triangle perimeter and area. It provides definitions and interactive animated activities that enhance further explanation.