At 20 seconds, the teacher says that the expressions 3y + 40 and 3x - 70 are equal, but actually they are supplementary, so (3y + 40) + (3x - 70) = 180. Again at 2:35, he says that 3y + 40 = 110, but because the angle are supplementary, you should have 3y + 40 + 110 = 180.
In this lesson, we learn how to find angles in a trapezoid by using alternate interior and corresponding angle theorems. The instructor takes us through a step-by-step process of finding the value of y and x in the given problem. By extending parallel lines and transversals, we can use same side interior angles to calculate the missing angles. By the end of the lesson, we have learned how to solve for variables and angles in a trapezoid.
Finding the values of variables to find angles in a trapezoid by using alternate interior and corresponding angle theorems.
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