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)
Pythagorean theorem - Answer a^2 + b^2 = c^2

Circumference of a circle - Answer C= (3.14)(d)

Area of a circle - Answer A=(3.14)(r^2)

distance formula - Answer D=(r)(t)

arithmetic sequence formula (explicit) - Answer an = a1 + (n - 1)d

Sum of arithmetic sequence - Answer S = (n/2) (a1 +(a1+(n-1)d)) or S = (n/2) (a1 + an)

Geometric sequence formula - Answer an=a1(r)^n-1

Geometric Series formula Finite - Answer Sn = a1 (1-r^n) / (1-r)

Combination formula - Answer nCr=n!/r!(n-r)

Permutation - Answer nPr=n!/(n-r)!

parabola - Answer y=a(x-h)^2+k

circle - Answer (x-h)^2+(y-k)^2

ellipse - Answer ((x-h)^2/a^2) + ((y-k)^2/b^2)= 1

hyperbola - Answer ((x-h)^2/a^2) - ((y-k)^2/b^2)= 1

Inscribed angle - Answer IA=central angle(or intercepted arc)/2

Property of Parallelogram - Answer Opposite sides are parallel and congruent
opposite angles are congruent
consecutive angles are supplementary
diagonals bisect each other

Property of Rectangle - Answer 4 90 degree angles

Property or Rhombus - Answer 4 congruent sides

Property of Square - Answer 4 90 degree angles and sides