,alternate interior, alternate exterior, or consecutive interior angles. 18. ∠5 and ∠1 20. ∠6 and ∠13 22. ∠2 and ∠11 19. ∠11 and ∠13 21. ∠10 and ∠15 23. ∠8 and ∠4

To find the inverse of a number a, one can use the equation f(c) = a-1/c=0 where c is the inverse of a use the secant method of finding roots of equations to find the inverse of a = 2.5 ,er = 0.001%