Sum and Difference Formulas New Identities. Cosine Formulas.
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Formulas
Section 3.7
Formula
•A formula is an equation that relates two or more real-life quantities.
•Don’t Write--You can solve a formula to describe one quantity in terms of the
others.
Using the Distance Formula
In other words SOLVE FOR r
d=rt
d = rt
Find a formula for r in terms of d and t.
d rt
tt
dr
t
Now Use the new formula to find the rate if you drive 400 miles for 5.5 hours. (nearest tenth)
dr
t
400 miles
5.5 hoursr
72.7 mi
rhr
Using an Area Formula
In other words SOLVE FOR l
A=lw
A = lw
Find a formula for l in terms of A and w.
lwA
ww
lw
A
Now Use the new formula to find the length of a rectangle with an area of 35ft2 and a width of 7 ft.
lw
A
lft
ft
7
35 2
lft 5
Simple Interest
Pt
t
Pt
I Pr
tI PrSolve for r.
What is my rate for an investment of $1500 if it made $54 in interest for one year?
rPt
I
54
(1500)(1)r
.036 r 3.6%
1. L = V - WH
2.
3.
4.
The formula for the volume of a rectangular prism is V = LWH. Which
equation solves the formula for L?
LV H
W
LV W
H
LV
HW
1. h = 3Vb
2.
3.
4.
The formula for the volume of a pyramid is V = . Which equation
solves the formula for h?
1
3bh
h 3b
V
h 3V
b
h V
3b
Solving a function for y…
43 yx Rewrite the equation so
that you isolate the y
variable
-3x -3x
xy 34
Solve for y: 4x – 2y = 12
1. Subtract 4x from both sides
2. Simplify
3. Divide both sides by -2
4. Does it simplify?
- 4x - 4x
-2y = –4x+12
-2 -2
y = 2x - 6
Practice… Solve for y
2 5
2 10
5 3 8 2
x y
x y
y x x
2 5
2 10
8
5
y x
x y
xy