Question

help please

Answer 1

With?

Answer 2

well you can use the law of cosines to check

do you know how to use it..?

Answer 3

no i dont :(

Answer 4

sec let me see what i can remeber :)

Answer 5

k

Answer 6

http://mathworld.wolfram.com/LawofCosines.html

Answer 7

im to lazy to draw the abc triangle lol, but that explains the law of cosines well

Answer 8

the law of cosines says

\[Cos(A) = \frac{b^2 = c^2 - a^2}{2bc}\]

does that help

Answer 9

you have

a = 5.3, b = 7 and c = 4... plug them in and post the answer you get

Answer 10

oops should read

\[\cos(A) = \frac{b^2 + c^2 - a^2}{2bc}\]

Answer 11

^

Answer 12

oh wait is it true?

Answer 13

ill leave it to him, he knows what he is doing :)

Answer 14

oh he left...

Answer 15

well why do you think it is true?

Answer 16

he did the "hard" part the rest is algebra

Answer 17

well you need to find the angle measure using the law of cosines to see if its true or not

Answer 18

an alternative solution is to google a triangle solver

put in the 3 sides and then look at the angles that are calculated

Answer 19

which law of cosine should i use

Answer 20

if only i wouldve thought of this when i was taking pre-calc...

Answer 21

use the one I posted above

Answer 22

how do i use it....do i sub

Answer 23

and look for the measures that match the labels a, b and c

Answer 24

a = 5.3 b = 7 and c = 4

like this

\[cos(\theta) = \frac{7^2 + 4^2 - 5.3^2}{2 \times 7 \times 4}\]

Answer 25

doin the math.....

Answer 26

\[\cos \theta \frac{ 49+16-28.09 }{66 }\]
thats what i have so far

Answer 27

is it right

Answer 28

so far

Answer 29

well I think the denominator is 56

Answer 30

2 x 4 x 7 = 56

Answer 31

oh yea

Answer 32

wait so it is true?

Answer 33

not yet, if you do the calculation you'll find

\[\cos(\theta) = 0.659107\]

so to find the angle, using a calculator its

\[\theta = \cos^{-1}(0.659107)\]

Answer 34

i got 0.79053943 ? how do i punch this equation in a calculator