6. The process of evaluating a definite integral by using the definition f(x)dx = lim h[f(a) + f(a + h) + (a + 2h) + (a + 3h) + ... + f(a+n-1h] is called integration h0 from first principles or integration by limit of a sum. method or integration as the 7. 13+2+3+ --+ (n1) =[n(n1)]* = 8. cosa + cos(a + h) + cos(a + 2h)+...+ cis[a+(n1)h]= 9. 1+2 +3 +...+(n1)="(n-1)(2n-1) 6 10. 13+2+3+...+(n-1): + (n1)=[n(n1)]*.