# Tutor.com Trigonometric Functions Session

##### Jul. 31, 2012

Session Transcript - Math - Trigonometry, 7/30/2012 4:43PM - Tutor.comSession Date: 7/30/2012 4:43PM
Length: 17 minute(s)
Subject: Math - Trigonometry

System Message
[00:00:00] *** Please note: All sessions are recorded for quality control. ***

Jenna (Customer)
[00:00:00] Which of the following statements are true? (i) the law of sines should be used when ASA is given. (ii) the law sines should be used when SAS is given. (iii) the law of sines should be used when AAA is given.

Lauren R (Tutor)

Jenna (Customer)
[00:00:18] i need help with this problem

Lauren R (Tutor)
[00:00:22] ok
[00:00:43] so we are working with the law of sines, do you know what the equation is for law of sines?

Jenna (Customer)
[00:01:09] yes i do

Lauren R (Tutor)
[00:01:20] ok can you put it on the board?
[00:02:24] awesome,
[00:02:43] so now we need to determine which works for law of sines, ASA, SAS or AAA

Jenna (Customer)
[00:02:50] right

Lauren R (Tutor)
[00:03:14] one of them sticks out as not being able to work at all, do you hvae any ideas which one that is?

Jenna (Customer)
[00:03:41] hmmm is it SAS
[00:03:42] ?

Lauren R (Tutor)
[00:04:07] Well, let's look at the formula, in order to use the formula you need to have both one angle and one side correct?

Jenna (Customer)
[00:04:18] correct

Lauren R (Tutor)
[00:04:32] ok, so which one doesnt give me any information about sides?

Jenna (Customer)
[00:04:50] AAA

Lauren R (Tutor)
[00:04:55] exactly, so that one is out

Jenna (Customer)
[00:05:10] oh okay

Lauren R (Tutor)
[00:05:26] NOw let me draw two triangles each one with asa and one with sas, and lets see if we can figure out which one will work
[00:07:50] ok, in order to use law of sines we need to have one pair that is a side and angle

Jenna (Customer)
[00:08:06] oh okay

Lauren R (Tutor)
[00:08:51] because we need to have one ratio that is all numbers, so one one of these triangle can give me a pair (side a, A or side b, B, or side c, C)

Jenna (Customer)
[00:09:09] oh okay

Lauren R (Tutor)
[00:09:32] Now if I look at both of them, nothing is paired, there is no angle that I alsop have a side to, however...
[00:09:40] one of them can get me to the information I need

Jenna (Customer)
[00:09:51] oh okay

Lauren R (Tutor)
[00:10:14] Given a triangle that is not a right triangle, what can I find, the third side, or the third angle?

Jenna (Customer)
[00:10:29] im not sure.

Lauren R (Tutor)
[00:10:47] ok let's try this...
[00:11:00] can you find the measure of angle c in this first triangle?

Jenna (Customer)
[00:11:20] is it 58?

Lauren R (Tutor)
[00:11:29] yep
[00:11:42] can I use law of sines with this now?

Jenna (Customer)
[00:11:44] im sorry to just leave in the middle of this but ive got to go

Lauren R (Tutor)
[00:11:54] we are at the answer,
[00:11:59] but if you need to leave that is fine

Jenna (Customer)
[00:12:04] oh we are? never mind continue

Lauren R (Tutor)
[00:12:25] Look at what we have now in this triangle, we have side c and angle C
[00:12:27] a pair
[00:12:35] I can use law of sines now with this triangle

Jenna (Customer)
[00:12:39] right

Lauren R (Tutor)
[00:12:55] which was the given information ASA or SAS?

Jenna (Customer)
[00:13:19] both were given.

Lauren R (Tutor)
[00:13:46] That first triangle, which information lead me to using law of sines
[00:13:55] was it labeled ASA or SAS

Jenna (Customer)
[00:14:01] ASA

Lauren R (Tutor)
[00:14:05] There ya go!
[00:14:20] here is a hint:

Jenna (Customer)

Lauren R (Tutor)
[00:14:23] 1. Use the law of cosines when you are given SAS, or SSS
[00:14:31] 2. Use the law of sines when you are given ASA, SSA, or AAS
[00:14:45] Yes ASA will let me use law of sines, because I can find the missing angle to make my pair

Jenna (Customer)
[00:15:11] so SAS doesnt use the law of sines?

Lauren R (Tutor)
[00:15:27] nope, nothing matches, I have side b, angle C and side a
[00:15:42] since the triangle is not right I cant find the third side, or find any of the other angles

Jenna (Customer)
[00:15:47] oh okay!

Lauren R (Tutor)