# How to Evaluate Trigonometric Functions

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Evaluating trigonometric functions means dealing with a shape like a right triangle. Evaluate trigonometric functions with help from an experienced mathematics educator in this free video clip.

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## Video Transcript

Hi, my name is Marija, and today I'm going to show you how to evaluate trigonometric functions. So if we are dealing with trigonometric functions that means that we must have a right triangle. So we will use the right triangle 3, 4, 5 and we'll use this angle here as our theta. So the three trig functions that we are going to evaluate today are sine, cosine and tangent. So if we are looking for the sine of theta, then what we're going to have to remember is the little phrase sohcahtoa. So if you haven't learned it yet in trig, this stands for sine is opposite over hypotenuse. So this is our first trig function here. Sine is opposite over hypotenuse. So if I am looking for the sine of theta I'm looking for the opposite side which is 3 over the hypotenuse which is 5. So the sine of theta becomes 3/5ths. The next three letters give me the cosine function. The cosine is equal to the adjacent over the hypotenuse. So if I am doing the cosine of theta I'm looking for the adjacent side which is the 4 over the hypotenuse which is the 5. And lastly if I'm doing tangent, I'm looking at the last three letters and it tells me that the tangent is equal to the opposite over the adjacent. So the opposite again is going to be my 3 and the adjacent is going to be my 4. So by remembering sohcahtoa you can evaluate all three of your trig functions on any given angle.

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