The formula D=241 cos1(tan i tan ) can be used to approximate the number of hours of daylight when the declination of the Sun is i at a location north latitude. To use the formula, cos1(tan i tan ) must be expressed in radians. Approximate the number of hours of daylight in Sioux Falls, South Dakota 4333 north latitude), on (a) the summer solstice (i=23.5), (b) the vernal equinox (i=0), and (c) July 4 (i=2248)