ACT Math Tips

radians > degrees

radians > degrees

multiply by 180/pi

degrees > radian

pi/180

odd-odd=

always even

GCF

greatest number that is a factor of both numbers

LCM

least number that is a multiple of both numbers

decimal to fraction on CALC

MATH > FRAC

Multiplying and dividing fractions

multiplying - multiply numerators and dominators (¾ x 5/6 =15/24 =5/8)

dividing - multiply first fraction by the reciprocal of second (¾ / 5/6 × =3/4 × 6/5= 18/20 = 9/10)

compound interest

A = P (1+r/n)^nt

simple interest

A=P(1+rt)

multiplying and dividing powers with the same base

multiplying - add the exponents

dividing - subtract the exponents

rationalizing radical expressions

equation of circle

(x-h)²+(y-k)²=r²

center - (h,k)

volume of rectangle

l•w•h

volume of sphere

4/3 pi r³

volume of right cylinder

pi r² h

special right triangles

Pythagorean Theorem

a²+b²=c²

area of parallelogram

bh

Area of triangle

1/2(bh)

area of circle

pi r²

similar triangles

area of trapezoid

(b1+ b2)2h

perimeter

add up all sides

circumference of circle

2 pi r

area of right cylinder

pi r² h

point slope formula

(y2-y1)/(x2-x1)

vertex form

a(x-h)²+k

standard form

ax²+bx+c

law of sines

sin A/a

sin B/b

sin C/c

SOH CAH TOA

SOH - sin: opp/hyp

CAH - cos: adj/hyp

TOA - tan: opp/adj

imaginary numbers

i= _/-1

i²= -1

i³= -i

i^4= 1

change of base formula

log_b x = logx/logb

quadratic formula

x= -b ± _/b²-4ac/ 2a

mid point formula

distance formula

standard form of line

Ax+By=C

slope of standard form

-A/B

volume of cylinder

1/3 pi r² h

sin A = cos B

sin B = cos A

sin A = cos (90-A)

cos A = sin (90-A)

how many different arrangements

1×2×3×4×5 etc.