Unknown Side Lengths in Right Angle Triangles - SOH CAH TOA(Trigonometric Ratios)In this section we learn how to use SOH CAH TOA to find unknown side lengths in right angle triangles. Show
What You'll find here:
MethodGiven a right angle triangle, the method for finding an unknown side length, can be summarized in three steps:
Scenario 1: unknown side, \(x\), on the numeratorThe first scenario we learn about is the one illsutrated here.
(\(x\) is on the numerator)
Notice that in the first scenario the unknown side length \(x\) was on the numerator, of the trigonometric ratio. Indeed we had \(sin(29)=\frac{x}{8}\). Tutorial 1:In the following tutorial we learn how to deal with the simpler scenario in which the unknown side length ends-up on the trigonometric ratio's numerator.
This makes the required algebra, for finding \(x\), relatively simple (all we had to do was multiply by \(8\) to find an expression for \(x\)). We'll be seeing, in scenario 2, that this won't always be the case. Indeed, in the more complicated cases: \(x\) will be on the denominator and it will require a little more algebra to find an expression for \(x\). Scenario 2: unknown side, \(x\), on the denominatorThe second scenario we learn about is the one illsutrated here.
Notice that in the first scenario the unknown side length \(x\) was on the numerator, of the trigonometric ratio. Indeed we had \(sin(29)=\frac{x}{8}\). This makes the required algebra, for finding \(x\), relatively simple (all we had to do was multiply by \(8\) to find an expression for \(x\)). We'll be seeing, in scenario 2, that this won't always be the case. Indeed, in the more complicated cases: \(x\) will be on the denominator and it will require a little more algebra to find an expression for \(x\). \(x\) is on the denominatorTutorial 2:In the following tutorial we learn how to deal with the simpler scenario in which the unknown side length ends-up on the trigonometric ratio's numerator.
If you feel confident to start working on exercises now, scroll down to work through the exercise further down. Otherwise make sure to watch this "summary" tutorial, in which we review the two methods for finding uknown side lengths in right angle triangles. Tutorial 3: Summary - Finding Unknown Side Lengths using SOH CAH TOA
Exercise 1In each of the following right angle triangles, find the unknown side length marked x: Note: this exercise can be downloaded as a worksheet to practice with: Worksheet 1 Solution Without Working
Tutorial 2: the "trickier scenario"In the following tutorial we learn how to deal with the scenario in which the unknown side length ends-up on the trigonometric ratio's denominator.
Exercise 2In each of the following right angle triangles, find the unknown side length marked x: Note: this exercise can be downloaded as a worksheet to practice with: Worksheet 2 Solution Without Working
How do you solve a non right triangle with one side and one angle?The Law of Sines can be used to solve oblique triangles, which are non-right triangles. According to the Law of Sines, the ratio of the measurement of one of the angles to the length of its opposite side equals the other two ratios of angle measure to opposite side.
How do you find the 3rd side of a triangle?When we're trying to find the hypotenuse we substitute our two known sides for a and b. It doesn't matter which leg is a and which is b. Then we solve for c by adding the squared values of a and b and taking the square root of both sides.
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