In triangle ABC, angle C is 90 degrees, AB = 18, cosA = 0.5. Find AC.

1) If cos A = 0.5, then the angle A is 60 °. Let’s find the value of the third angle of the figure, given that they all add up to 180 °:

180 – (90 + 60) = 30 (°).

2) Using the theorem of sines, the dependence is true:

AB / sinC = AC / sin B.

From the formula we have a relation for finding the unknown side of the AU:

AC = AB * sin B / sin C.

Since it is known that sin 30 ° = 1/2, Sin 90 ° = 1, and AB, according to the problem statement, is equal to 18, we obtain that the value of the AC side is equal to :.

AC = (18 * 1/2) / 1 = 9.

Answer: the side of the triangle is AC = 9.