To find the height of the triangular sides of a rectangular pyramid when calculating the surface area, you would use the vertical height of the pyramid, which is usually given as a separate dimension. Without knowing the specific dimensions provided, I cannot determine which dimension to use. However, if the height of the pyramid is given, you would use that value.
In general, the formula for calculating the surface area of a rectangular pyramid is given by:
Surface Area = 2*(base area) + (perimeter of base) * (slant height)
where the base area is the area of the base of the pyramid, and the slant height is the height of one of the triangular sides.
To find the height of the triangular sides, you can use the Pythagorean theorem. If the base of the pyramid is a rectangle, you can consider the base of the pyramid as one of the legs of a right triangle, the slant height as the hypotenuse, and the vertical height of the pyramid as the other leg.
Therefore, you can use the Pythagorean theorem to find the height of the triangular sides:
(vertical height)^2 + (base/2)^2 = (slant height)^2
Once you have found the height of the triangular sides, you can use it in the surface area formula mentioned above to calculate the total surface area of the rectangular pyramid.