someone please explain how to solve this
Given ΔABC, m∠A = 60°, b = 9 and c = 6. Find m∠B. Round to the nearest whole degree.
A)
8°
B)
41°
C)
71°
D)
79°

- anonymous

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- anonymous

do you know the law of sines?

- anonymous

its something like soh cah toa

- anonymous

you can only use that if you know it's a right triangle

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## More answers

- anonymous

it is soh cah toa

- anonymous

how about a/sinA=b/sinB=c/sinC

- anonymous

but which side is which

- anonymous

i dont know theres no picture

- anonymous

so try soh can toa, do you know what it stands for?
*tip: c usually= hypotenuse

- anonymous

cah sorry not can

- anonymous

well then why is b bigger than c

- anonymous

@tlatti

- anonymous

no i dont understand th esoh cah toa i looked it up and i dont understand

- anonymous

Sine
Opposite
Hypotenuse
Cosine
Adjacent
Hypotenuse
Tangent
Opposite
Adjacent

- anonymous

|dw:1433517992401:dw|

- MrNood

you do not know that this is a right angle so you cannot use the standard trig functions

- anonymous

what im so confused

- anonymous

then what do i use

- MrNood

|dw:1433518102874:dw|
the general triangle is drawn above

- anonymous

how do you solve it

- MrNood

|dw:1433518184180:dw|

- MrNood

so
FIRST
use law of cosines to find a
a^2 = b^2 + c^2 -2bc cosA
then
use law of sines
a/sinA = b/sinB

- anonymous

uhh can you show me?

- anonymous

im still a little lost

- anonymous

@MrNood

- MrNood

The equations you need are above, and the values of a,b and A are given in the question and in my drawing
this question is about cosine and sine rules
use them to solve as described above
FIRST solve a from cosine rule
THEN solve B from sine rule

- anonymous

so for a i got 6210?

- MrNood

given that the other 2 sides ar 6, & 9 is that a likely answer?

- anonymous

no thats y im so confused i dont know where im going wrong

- MrNood

a^2 = b^2 + c^2 -2bc cosA
you are trying to find a
first write down
what is b
what is c
what is cos A

- anonymous

b is 9 9^2 is 81

- anonymous

c is 6 6^2 36

- MrNood

ok good
soo ... 2bc cosA =??

- anonymous

cosA is 0.5

- anonymous

2bc cosA= 2916?

- MrNood

2* 9 * 6 * 0.5 =

- anonymous

54

- anonymous

i thought we were supposed to use the squared number like 81 nd 36

- MrNood

a^2 = b^2 + c^2 -2bc cosA
the squared numbers are part of it - but not in the 2bc cos A

- anonymous

so do i plug in the numbers to the equation? @MrNood

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