Isosceles is a trapezoid in which the sides are equal:
AB = CD.
Since the bases of the trapezoid are parallel, the heights of the trapezoid are equal to each other:
BE = CF.
In order to find the length of the height BE, consider the triangle ΔABE.
Since we know the value of the angle ∠ABE and the length of the hypotenuse AB, we will use the cosine theorem to calculate BE:
cos B = BE / AB;
BE = AB cos B;
cos 30º = 0.866;
BE = 4 · 0.866 = 3.464 ≈ 3.5 cm;
CF = BE = 3.5 cm.
Answer: The length of the CF height is 3.5 cm.
One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.