# Triangle trig

## Re: Triangle trig

If a graphing calculator is allowed, you can simply graph 3sin(x) and 2tan(90-x), which intersect in only one place within 0<x<90, x=60. So B=60 degrees and A=90-60=30 degrees.

Otherwise, you have:

B=90-A

2sin(90-A)=3tan(A)

2cos(A)=3tan(B)

2cos(A)=3sin(A)/cos(A)

2cos

2(1-sin

From here, you can substitute u=sin(A), solve the quadratic equation for u, then take the sin

Otherwise, you have:

B=90-A

2sin(90-A)=3tan(A)

2cos(A)=3tan(B)

2cos(A)=3sin(A)/cos(A)

2cos

^{2}(A)=3sin(A)2(1-sin

^{2}(A))=3sin(A)From here, you can substitute u=sin(A), solve the quadratic equation for u, then take the sin

^{-1}for whatever answer works, and I'm guessing you'll get A=60 degrees.**bfrsoccer**- Administrator
- Posts : 61

Join date : 2008-11-09

## Re: Triangle trig

alrite, some problems here:

2sin(90-A)=3tan(A)

2cos(A)=3tan(B)

-on the left side, how do you change sin to cos like that?

similarly....

2cos

2(1-sin

-the LS again, what did you do to get that?

3rd: what u?, when you say u=sinA?

and lastly, last line i think you mean A = 30

and those are the only problems i have.

thanks!

2sin(90-A)=3tan(A)

2cos(A)=3tan(B)

-on the left side, how do you change sin to cos like that?

similarly....

2cos

^{2}(A)=3sin(A)2(1-sin

^{2}(A))=3sin(A)-the LS again, what did you do to get that?

3rd: what u?, when you say u=sinA?

and lastly, last line i think you mean A = 30

and those are the only problems i have.

thanks!

**karooomph**- Posts : 74

Join date : 2008-11-19

Age : 22

Location : ubseikastan

## Re: Triangle trig

"on the left side, how do you change sin to cos like that?"->It's a trigonometric identity for sin(a-b)

"-the LS again, what did you do to get that?"

sin

1-sin

"what u?, when you say u=sinA?" 2(1-sin

Literally substitute u=sin(A) into the equation and solve: 2(1-u

Then, once you have u, you can find a because you know u=sin(A)

"and lastly, last line i think you mean A = 30" er, oops, yeah, I meant 30

"-the LS again, what did you do to get that?"

sin

^{2}(x) + cos^{2}(x) = 1; identity1-sin

^{2}(x)=cos^{2}(x)"what u?, when you say u=sinA?" 2(1-sin

^{2}(A))=3sin(A)Literally substitute u=sin(A) into the equation and solve: 2(1-u

^{2})=3uThen, once you have u, you can find a because you know u=sin(A)

"and lastly, last line i think you mean A = 30" er, oops, yeah, I meant 30

**bfrsoccer**- Administrator
- Posts : 61

Join date : 2008-11-09

## Re: Triangle trig

ic now, thanks, bfrsoccer

**karooomph**- Posts : 74

Join date : 2008-11-19

Age : 22

Location : ubseikastan

## Re: Triangle trig

[quote]2cos(A)=3tan(B)

I think you meant tan(A).

**karooomph**- Posts : 74

Join date : 2008-11-19

Age : 22

Location : ubseikastan

**caseycolin**- Posts : 29

Join date : 2010-07-29

## Re: Triangle trig

Hi,

There seems to be a problem with the bbcode for Googlevideo using full URL. Has anyone else noticed this?

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There seems to be a problem with the bbcode for Googlevideo using full URL. Has anyone else noticed this?

I cappied and pasted the BBcode and html replacements in the relevant sections but nothing happens when i insert a video using the bbcode.

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**LeeRain**- Posts : 12

Join date : 2010-09-10

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