If a + b + c = 0 then prove that cosa/2 + cosb/2 + cosc/2 = 4 cos (pi-a/4) cos (pi-b/4) sin (pi-c/4) ​

The sum of two numbers is 12 and their difference is 18 what are the two numbers

Aresearch group wants to find the opinions’ of city residents on the construction of a new downtown parking garage. what is the population of the survey downtown shoppers downtown visitors downtown workers city residents

X+ y = 5 ; x - y =3 solve using linear combination