Methods to Find Angles and Sides in a Triangle

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There are multiple methods that can be used to find the sides and angles of a triangle, such as Special Right Triangles (30, 60, 90 and 45, 45, 90), SOHCAHTOA, and the Law of Sines and Cosines. These methods are very helpful. I will explain how to use all three of them with examples at the end. The first example, Special Right Triangles, is used only with right triangles. To use this method, you need to have angle measures of 30, 60, and 90, or 45, 45, and 90. There is a "stencil" that goes with these degrees. In the 30-60-90 triangle, the side opposite the 30 degrees is "S". The side opposite the 90 degrees is "2S". Lastly, the side opposing the 60-degree angle is "S radical 3". Let's say you were given "S". You would multiply that by two to find the value of the side opposite the 90 degrees. To find the side corresponding with 60 degrees, you then take the value of "S" and set it equal to "S √3". Then you would have to move the radical three over to the other side. Finally, you divide by three to get the answer. With a 45-45-90 triangle, the side corresponding with the 90 is s√2. The sides corresponding with the 45-degree angles are both "S". Next, we have the acronym SOHCAHTOA. A way to remember it is: "Some Old Hippie Caught Another Hippie Tripping On Acid." This method is used to find angles when given the sides of a triangle, unlike Special Right Triangles. The acronym stands for sine (opposite divided by the hypotenuse), cosine (adjacent divided by the hypotenuse), and tangent (opposite divided by adjacent). This method can also only be used with right triangles. When doing a problem like this, it will state which method you should use (sine, cosine, or tangent). Let's start with sine first. Sine is listed above as OPPOSITE ÷ HYPOTENUSE. The side corresponding with the 90-degree angle (the only angle given) is always the hypotenuse of the triangle. The angle you are solving for is “X,” and its corresponding side is always the opposite side of the triangle. Whichever side is left is the adjacent side. Then you do opposite over hypotenuse to get the degree of “X.” Since all triangles equal 180 degrees, you can then find the third degree by adding the two given degrees and subtracting that by 180.

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