Question

Solve the triangle
a = 12, b = 14, c = 21

Answer 1

Apply law of Cosines to find the angle!

Answer 2

how do you do that?

Answer 3

Post the formula, I'll show you :)

Answer 4

c^2 = a^2 + b^2 – 2ab cos C
and
a^2 = b^2 + c^2 – 2bc cos A
and
b^2 = a^2 + c^2 – 2ac cos B.

Answer 5

a² = b² + c² – 2bc cos A
->cosA = ( b² + c² - a² ) / 2bc

Answer 6

how did you change that?

Answer 7

We find the angle, so we need to switch around :0

Answer 8

okay so a would be
84 degrees?

Answer 9

How???

Answer 10

Don't just give me your result, because I don't have the power to read your mind :P

Answer 11

(14^2+21^2-12^2)=493
493/2bc
2bc=2*14*21=588
493/588=0.838
since we are finding degrees
that would be 84 degrees
right?
and sorry lol

Answer 12

My calculator shows 33° !

Answer 13

How did you do that?
im confused i used my graphing calculator......

Answer 14

A = arccos (.838) =

Answer 15

what is arccos?

Answer 16

oh nvm i found
it...

Answer 17

inverse of cos to find the angle :0

Answer 18

okay so the how would we find B?

Answer 19

Now, use sines law to find the second angle!

Answer 20

b^2 = a^2 + c^2 – 2ac cos B.
or
cos B=(a^2+c^2-b^2)/2ac
right?

Answer 21

oh
sin A/a = sin B/b = sin C/c

Answer 22

yes,
SinB = b sinA/a

Answer 23

Sin B= 14*sin(33 Degrees)/12
Sin B=14*.045
Sin B= .635
B= 39 degrees?

Answer 24

Yup, I can see you make great progress =)

Answer 25

And C would be Law of Sines too?

Answer 26

No, C = 180° - ( A + B) = ...

Answer 27

oh okay
you just add the two angle and subtract because it is the only angle left in the triangle...
So...
C=180 degrees -(33+39)
C= 180 degrees - 72 degrees
C= 108 Degrees

Answer 28

I have three more solve the triangle problems but they are different... will you help... PLZ

Answer 29

C= 107.39°

Answer 30

Just open the new post, I'll follow up :)

Answer 31

Okay THANK YOU SO SO MUCH!!!!!!!!!!!!!!!!!!!!