Quandaries and Queries
 

 

hey my name is kerri i'm a college students and i was wondering if you could help in with this problems

sin2x-5sinx-3=0

 

 

Hi Kerri,

A great deal of algebra has to do with "pattern recognition". It's like hearing the first chord in a song and knowing who is doing it, even if you have never heard that cut before. no one else makes that sound!

When you show me

sin2x-5sinx-3=0

I see a trinomial

(something)2 - 5 (the same something) - 3 = 0

To do it in a more formal way, let y = sinx then your equation is

y2 - 5 y - 3 = 0

Solve for y. (This doesn't factor so you will have to use te general quadratic.) You will get two possible values for y, a and b. Now you have

sinx = a and sinx = b

Since a and b are sine values they must be between -1 and 1. One of them is not and thus you are left with

sinx = a

What is x?

Penny

 
 

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