This is so confusing

newatthis · science forum beginner Joined: 02 May 2005 Posts: 48

hi

Trigonometry is really giving me troubles . Anyhow , question is related to trigonometry equations

sin x=a only when |a|<=1

First solution is from interval [-PI/2 , PI/2] -> x=arcsin a ;

Since sine function has period 2*PI ,the equation has infinite number of solutions :

x=arcsin a + k*2*PI ;

Sine also has the same value at angles :

x=PI-arcsin a +k*2*PI ;

So if sin x=0.5 then solutions are
x1=30 + k*360 and x2=150 + k*360

To my question:
- if sin x=-0.5 Then x1=-30 + k*360 ;

But how do I specify angle -150 with

x = PI-arcsin a +k*2*PI formula ?

I mean , instead of -150 I get angle 210 :

x2=180 - (-30) + k*360 = 210 +k*360 ?

thank you

Guest · Posted: Sat May 21, 2005 8:19 pm Post subject: Re: This is so confusing

newatthis wrote:

newatthis · science forum beginner Joined: 02 May 2005 Posts: 48

thank you very much

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