The law of cosines is used to find the measure of z. 162 = 182 + 192 – 2(18)(19)cos(z) 256 = 324 + 361 – (684)cos(z) 256 = 685 – (684)cos(z) –429 = –(684)cos(z) to the nearest whole degree, the measure of z is degrees.

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?