CK-12 Foundation
Alternate Formula for the Area of a Triangle: Alternate Area of a Triangle
It's always nice to have a plan B. Pupils investigate an alternate formula for the area of a triangle that uses sine. A set of challenge questions shows how the new formula relates to the well-known formula of (1/2)bh.
EngageNY
An Area Formula for Triangles
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....
EngageNY
Using Trigonometry to Determine Area
What do you do when you don't think you have enough information? You look for another way to do the problem! Pupils combine what they know about finding the area of a triangle and trigonometry to determine triangle area when they don't...
Alabama Learning Exchange
Triangle Area: No Height? Use the Sine
No height? No problem! Learners use their knowledge and a little help from GeoGebra to develop the Law of Sines formula. The Law of Sines helps to determine the height of triangles to calculate the area.
CK-12 Foundation
Determination of Unknown Triangle Measures Given Area: Jib Sheets
Solving triangles is a breeze. Young boat enthusiasts solve problems involving triangles in the context of sails on a boat. They must apply different strategies, including the Law of Cosines and area formulas.
Curated OER
Area of Triangle Using Trigonometry
In this trigonometry learning exercise, students determine the area of triangles using the trigonometry ratios of sine, cosine, and tangent. This one-page learning exercise contains ten problems.
Mathed Up!
Sine and Cosine Rules and Area of Triangles
Learners discover how to find missing sides and angles using trigonometry. Scholars first watch a video covering the Law of Sines and Cosines, as well as the area formula for a triangle. To test their knowledge, they complete a worksheet...
Mathematics Vision Project
Module 5: Modeling with Geometry
Solids come in many shapes and sizes. Using geometry, scholars create two-dimensional cross-sections of various three-dimensional objects. They develop the lesson further by finding the volume of solids. The module then shifts...
Curated OER
A Special Relationship
Students discover the relationships of the lengths of the sides of right triangles and right triangles using a series of drawings on dot paper. They investigate and solve problems of standard (customary and metric units) and non-standard...
Alabama Learning Exchange
"I Saw the Sine"
Discover trigonometric ratios that complement each other. Using two videos, the activity introduces the trigonometric ratios. The class discovers the relationship between the sine and cosine of complementary angles.
Curated OER
Area of a Triangle
Students solve the area of triangles. In this precalculus lesson, students are given two sides of a triangle and asked to calculate the area. They apply the law of sine and the side-angle-side area formula to solve.
Curated OER
The Law of Sines
In this law of sines worksheet, students use the law of sines to find the missing measurement in a triangle. They determine the value of angles and the lengths of triangles. Students compute the area of triangles. This four-page...
Curated OER
Law of Sines and Cosines
In this sine and cosine worksheet, students solve given triangles using the law of sines and cosines. They determine the area of triangles. This three-page worksheet contains 12 multi-step problems.
Chapman University
A Pythagorean-Style Proof of the Sine Sum-of-Angles Formula
This well organized poster shows a step-by-step algebraic proof and related graphic. Understanding how formulas were derived, connects learners to the idea that the study of mathematics is continuous and cumulative. Learners will...
National Council of Teachers of Mathematics
Improving Archimedes' Method
For this Archmides' method instructional activity, students determine the area of a regular n-gon inscribed in a circle. They use sine and cosine functions to solve problems. This three-page instructional activity contains 4...
Curated OER
Law of Sines and Cosines
Students solve problems using sine and cosine. In this precalculus lesson, students apply the properties of sine and cosine to solve non-right triangle problems. They use Heron's Law to find the area of a shape.
Curated OER
Sine and Cosine
Students solve problems using sine and cosine. In this precalculus lesson, students solve word problems using sine and cosine. They identify where it is appropriate to laws of sine and cosine and where to use the Pythagorean Theorem.
Curated OER
Law of Sines and Law of Cosines
In this Pre-calculus/Trigonometry activity, students use the laws of sines and cosines to solve triangles. The four page activity contains thirteen problems. Answers are not included.
Mathematics Vision Project
Module 7: Modeling with Geometry
Model good modeling practices. Young mathematicians first learn about cross sections and solids of revolution. They then turn their attention to special right triangles and to the Laws of Sine and Cosine.
Curated OER
Trigonometry Worksheet
In this trigonometry worksheet, students use the law of sines to find the length of a missing side of a triangle. They prove trigonometric identity and use Heron's formula to find the area of a triangle. This two-page worksheet...
Curated OER
The Law of Sines
Students define the laws of sine as it relates to a right triangle. In this trigonometry lesson, students identify the properties of sine to help then find mixing sides of a right triangle. They also solve for the missing angles.
Curated OER
Trigonometric Triangles
In this trigonometry worksheet, students find the missing angle and sides given the 6 trigonometric values. There are 6 questions with an answer key.
Curated OER
Section 6.1-6.2 Precalculus: Trigonometry
In this trigonometry worksheet, students solve 15 triangle problems. Students use the law of sines and law of cosines to find the missing angles and side lengths of a triangles.
Texas Instruments
What's the Trig?
Learners determine the trigonometric relationships within a triangle as they construct a right triangle on the Ti-89. They find the sine, cosine, and tangent of various angles of their triangle construction.