Final answer:
To find the distance from the base of the tower to the keys in a 45 45 90 triangle, the cosine trigonometric ratio is typically used, as it relates the adjacent side to the hypotenuse at a given angle.
Step-by-step explanation:
To find the distance from the base of the tower to your keys using a 45 45 90 triangle, we can utilize trigonometric ratios. In a 45 45 90 triangle, we know that the two non-hypotenuse sides are of equal length, and the angles opposite those sides are both 45 degrees. Therefore, to find the distance from the base of the tower (which can be considered the adjacent side to the angle of elevation) to a point on the ground level (which is the side opposite the angle of elevation), you could use either sine, cosine, or tangent ratios because sin(45°) = cos(45°) = tan(45°). However, typically the cosine trigonometric ratio is used to find the adjacent side given the hypotenuse and the angle, so the answer would be B) Cosine. Remember, cosine of an angle in a right triangle is defined as the length of the adjacent side divided by the length of the hypotenuse.