Answer: -4.88691778Solution:1.Write down the number of degrees you want to convert to radians Given Degree = -280° The formula to convert degrees to radian measure is:Radian = degree x π/180 2. Multiply the number of degrees by π/180. Think of it like multiplying two fractions: the first fraction has the number of degrees in the numerator and "1" in the denominator, and the second fraction has π in the numerator and 180 in the denominator. -280 x π/180 = -280π/1803. Find the largest number that can evenly divide into the numerator and denominator of each fraction and use it to simplify each fraction. The largest number for 280 is 20.-280 x π/180 = -280π/180 ÷ 20/20 = -14π /9 4. Then multiply the numerator by 3.14159 because pi or π is equivalent to 3.14159, -14x 3.14159= -43.982265. To get the radian measure, we will divide -43.98226 by 9. -43.98226/9= -4.88691778