Find the cosine of the trapezoid angle if the base is 7 and 14 and the sides are 10.

If the sides of the trapezoid are equal, then the trapezoid is isosceles.
Draw two heights from the ends of the upper base to the lower base (forming a rectangle, one of the sides of which is the upper base of the trapezoid).
Also, two identical right-angled triangles were formed, where the bases are the lateral sides of the trapezoid. Let’s find the value of the lower legs of these triangles:
(14 – 7) / 2 – 7/2 = 3.5.
The cosine of the angle in a right-angled triangle is equal to the ratio of the adjacent leg to the hypotenuse. This means that the cosine of the acute angle of the trapezoid is:
cos = 3.5 / 10 = 0.35
Answer: 0.35