lawrence's blog

in this part i will go over chapter 7 sections 1 and 2. they are very simple but you need to know these formulas because you do use them in all the other chapters. if you havent learned by now when b rob said you need to know all of this stuff im sure everyone knows now. anyway i will start go over these to sections

SECTION 1

two units of measure: degrees and radians

convert degrees to rads is x pi/180

convert rads to degrees is x 180/pi


coterminal angles +/- 360 or +/- 2pi if in rads

to convert to minutes and seconds.

to convert to minutes and seconds you just multiply by 60

to get them out of minutes and seconds its

x/60 + y/3600

examples:

1) 315 degrees convert to rads

315 x pi/180
=7pi/4

2) 25.335 degrees convert to minutes and seconds

.335 x60= 20.1

.1 x60= 6

25 degrees 20' 6"

SECTION 2

these are the formulas

s=r theta
k=1/2 r squared theta
k= 1/2 rs

know s=arc length r=radius theta= central angles and k=area of a sector

theta must also be in radians!!!!!!!

example

1) sector of a circle has arc length 6cm& 75cm squared. find its radius and the measure of its central angle

s= 6cm k=75
r=? theta=?

75= 1/2r(6)
75=3r now you divide by 3

r=25cm dont forget the units


now you use s=r theta

6=25(theta)
theta= 6/25 rads

i hope this helped some people who may not totally get this and i hope those who didnt finally have it and i hope everyone had a great holiday break.