Углы при одном из оснований трапеции равны 80° и 10°, а отрезки, соединяющие середины противоположных сторон трапеции, равны 20 и 17. Найдите основания трапеции.
Q. Углы при одном из оснований трапеции равны 80° и 10°, а отрезки, соединяющие середины противоположных сторон трапеции, равны 20 и 17. Найдите основания трапеции.
Identify Properties and Information: Identify the properties of the trapezoid and the given information.We have a trapezoid with one pair of angles given as 80∘ and 10∘. The segments connecting the midpoints of the opposite sides (also known as the mid-segment or midline) are given as 20 and 17. The mid-segment of a trapezoid is parallel to the bases and its length is the average of the lengths of the bases.
Set Up Equation: Use the properties of the mid-segment to set up an equation. Let the lengths of the two bases be a and b, with a being the longer base. The mid-segment's length is the average of the two bases, so we have the equation (a+b)/2=20.
Solve for Base Length: Solve the equation for one of the bases.We can express b in terms of a by rearranging the equation: b=40−a.
Apply Second Mid-Segment Properties: Apply the properties of the trapezoid to the second mid-segment.The second mid-segment, which is 17, is not parallel to the bases. It is the segment that connects the midpoints of the non-parallel sides (legs) of the trapezoid. This segment forms two similar right triangles within the trapezoid, one on each side.
Find Ratio of Sides: Use the angles to find the ratio of the sides in the similar right triangles.The angles of 80∘ and 10∘ at the base create two right triangles with the angles 80∘, 10∘, and 90∘, and the other with angles 10∘, 80∘, and 90∘. The ratio of the sides opposite to the 10∘ and 80∘ angles will be the same as the ratio of the sine of these angles. However, this step involves a trigonometric approach that is not necessary for solving the problem, as we can use the properties of the mid-segment directly. Therefore, this step is a misstep.
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