Question

Trig / Geometry Question. Question in comments. Please Help

Answer 1

I would love to help! Just let me make sure I have the angles and sides correct. Angle A is 64, angle B is 85, and side c is 9.3. Yes?

Answer 2

Yes, That is correct. You can zoom in on the photo. It might help.

Answer 3

I'm good. Thanks. The first thing I would like you to do is find the measure of angle C. Can you do that?

Answer 4

Yes, The interior angles add to 180 so It must be 31 degrees,right?

Answer 5

Yes good! Now do you know the Law of Sines?

Answer 6

opposite / hyp. right?

Answer 7

No, that's the sin identity. The Law of Sines is the method you use in non-right triangles to find missing side and angle measures. It says this:\[\frac{ a }{ sinA }=\frac{ b }{ sinB }=\frac{ c }{ sinC }\]Those lowercase letters represent the side lengths and the capitol letters represent the angle measures. Let's fill in what we know now using what they have given us.

Answer 8

And you only need two of the above identities, you don't need all 3. You have angle C and side c and angle A but no side a. So we will solve for that first.

Answer 9

Ok, Now I know what your talking about. You see I am taking an online APEX class and they do not explain things very well. So that's why I turned to this site.

Answer 10

This site rocks! Us math nerds get to do math all day long and help others to understand it a bit better in the end!

Answer 11

:)thanks

Answer 12

The Law of Sines is used, like I said, in non-right triangles to find the missing measures of sides and lengths. Our set up to find side a is as follows. (Tell me you have a calculator...please tell me you have a calculator and that it is at least a TI 30 or higher).

Answer 13

i have an iphone.

Answer 14

Does it have sin, cos, tan?

Answer 15

Ok I got one!

Answer 16

Casio fx11es PLUS

Answer 17

Will that work

Answer 18

Oh my... ; ) Does it have the sin function on it?

Answer 19

yes it has like Rocket science stuff on it if i'm not mistaken

Answer 20

It has the Sin and Other stuff too

Answer 21

okay lets work through this!

Answer 22

Ok, good...sin I can do...rocket science I cannot! lol Here is the first set up using the Law of Sines for finding side a.\[\frac{ sinC }{ c }=\frac{ sinA }{ a }\]\[\frac{ \sin31 }{ 9.3 }=\frac{ \sin64 }{ a }\]We need to solve that for a. Can you solve it for a? We will do the math stuff on the calculator in just a minute. First, solve that for a =

Answer 23

\[A= 64 degrees?\]

Answer 24

oh the other a?

Answer 25

The way you solve an equation of this type is to cross-multiply. In other words,
a(sin31) = 9.3(sin64). Then divide away the (sin31) to isolate a like this: \[a=\frac{ 9.3(\sin64) }{ \sin31 }\]Do you know cross multiplication?

Answer 26

ok. Now do you multiply each side by the Sin?

Answer 27

Not quite. Now is where we do the math on our calculators! Do me a favor, find the sin64 on that calculator and tell me what you get. I need to make sure it's not in radians. Give me the answer for sin64.

Answer 28

0.8987940463

Answer 29

ok, good, it's in degrees. According to our equation above, we need to multiply the sin64 by 9.3 and then divide the whole thing by the sin31. So take your .89879 times 9.3 and what do you get?

Answer 30

8.35

Answer 31

Very good. Now divide it by sin31. you should be able to hit the divide key and it should say something like "ANS"/ then enter sin31 and hit equals. Tell me what you get now.

Answer 32

-8.5 after i clicked answer

Answer 33

Ok maybe 16,21

Answer 34

Something went wrong. 8.35/sin31-->8.35/.51503= what . Try it again.

Answer 35

Yes, it is 16.21! That, my dear friend, is the measure of side a.

Answer 36

Yay!

Answer 37

So Im guessing its 16.23 on the question becuase it says round 2 decimal places

Answer 38

Yay is right! Now we have to do the same thing for side b, using angle b, x for side b (cu we don't know it), let's use angle A and side a now for this one.

Answer 39

ok can you walk me through it again?

Answer 40

My bad...we have b we don't have a. And of course I will walk you through it! I'm not leaving til you're done with this problem.

Answer 41

I thought we had all the angles.

Answer 42

Ugh! We have a and not b; I wrote it in the wrong place on my triangle. Duh! We will do the Law of Sines again.\[\frac{ sinA }{ a }=\frac{ sinB }{ b}\]\[\frac{ \sin64 }{ 16.21}=\frac{ \sin85 }{ b }\]We do have all the angles, we are finding the side b.

Answer 43

b(sin64) = 16.21(sin85)

Answer 44

thats what i was about to say great!

Answer 45

Now we multiply each by sin85 right?

Answer 46

To isolate the b, you would divide both sides by sin64.

Answer 47

Ok let me do that: so 16.21/ sin64

Answer 48

Do it this way: Find sin85 on your calculator. What do you get?

Answer 49

.996

Answer 50

Now multiply that by 16.21 and what do you get?

Answer 51

16.145

Answer 52

Now divide that by sin64. And now what do you get?

Answer 53

17.96

Answer 54

Yep! And THAT, my dear friend, is the length of side b. Now you have all you need! Yay for you!

Answer 55

So the correct answer is D? on the

Answer 56

question?

Answer 57

Thank you for your help, May I ask what college did you attend?

Answer 58

Yes the answer is D. And I also just finished college online. Grand Canyon University. I just got done student teaching Algebra, Algebra 2, Trig, Geometry, and Calculus. I am going to be a high school math teacher.

Answer 59

You're welcome on the help thing!

Answer 60

Well congratulations! I hope that works out for you. I plan on attending Embry Riddle Aeronautical University. Thanks for the help. Let me fill in the answer

Answer 61

Do you think you could help me with another question? If its not too much to ask?

Answer 62

You'll be fine. Just practice with the Law of Sines; next will be Law of Cosines and that one is a bit trickier. Practice, practice, practice! I imagine you'll need lots of math in Aeronautical school!

Answer 63

I did that one first! It was a bit challenging.

Answer 64

scratch that idea. You have yourself a nice night Sir.