Given a right-angled triangle ABC, an angle C of a straight line. It is known that AC = 20, BC = 10. Find cos B.

1. By the Pythagorean theorem, it is known that the hypotenuse of a triangle is equal to the square root of the sum of the squares of the legs.

2. Let’s calculate the hypotenuse ab of the triangle abc, if it is known that the leg bc is 10 centimeters, and the leg ac is 20 centimeters.

ab = (bc ^ 2 + ac ^ 2) 1/2 = (10 ^ 2 + 20 ^ 2) 1/2 = 500 ^ 1/2 = 22.36 centimeters.

3. The cosine of an acute angle of a right-angled triangle is the ratio of the adjacent leg to the hypotenuse.

Find the cosine of the angle B.

cosB = bc: ab = 10: 22.36 = 0.45.

Answer: СsB is equal to 0.45. 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.