Need-to-Know ACT Math Formulas (Barrons)All the important and most forgotten formulas needed to know for the ACT

Need-to-Know ACT Math Formulas (Barrons)All the important and most forgotten formulas needed to know for the ACT Pythagorean theorem Correct Answer: a^2 + b^2 = c^2 Circumference of a circle Correct Answer: C= (3.14)(d) Area of a circle Correct Answer: A=(3.14)(r^2) distance formula Correct Answer: D=(r)(t) arithmetic sequence formula (explicit) Correct Answer: an = a1 + (n - 1)d Sum of arithmetic sequence Correct Answer: S = (n/2) (a1 +(a1+(n-1)d)) or S = (n/2) (a1 + an) Geometric sequence formula Correct Answer: an=a1(r)^n-1 Geometric Series formula Finite Correct Answer: Sn = a1 (1-r^n) / (1-r) Combination formula Correct Answer: nCr=n!/r!(n-r) Permutation Correct Answer: nPr=n!/(n-r)! parabola Correct Answer: y=a(x-h)^2+k circle Correct Answer: (x-h)^2+(y-k)^2 ellipse Correct Answer: ((x-h)^2/a^2) + ((y-k)^2/b^2)= 1 hyperbola Correct Answer: ((x-h)^2/a^2) - ((y-k)^2/b^2)= 1 Inscribed angle Correct Answer: IA=central angle(or intercepted arc)/2 Property of Parallelogram Correct Answer: Opposite sides are parallel and congruent opposite angles are congruent consecutive angles are supplementary diagonals bisect each other Property of Rectangle Correct Answer: 4 90 degree angles Property or Rhombus Correct Answer: 4 congruent sides Property of Square Correct Answer: 4 90 degree angles and sides Property of Trapezoid Correct Answer: one set of parallel sides isosceles trapezoid Correct Answer: one set of parallel sides and 2 congruent sides trigonometry functions Correct Answer: a sin (b(x-c))+d area of trapezoid Correct Answer: a= (b1+b2/2)(h) volume of a pyramid Correct Answer: B(length x width) x H volume of a cone Correct Answer: (1/3)(pi)(r^2)(h) volume of a cylinder Correct Answer: (pi)(r^2)(h) volume of sphere Correct Answer: 4/3(pi)(r^3) volume of rectangular prisim Correct Answer: b x w x h sum of angles in polygon Correct Answer: n=(n-2)(180) single interior angle Correct Answer: n= (n-2)(180)/n