# Trig Equations

• Jan 1st 2013, 01:45 PM
xoxo
Trig Equations
Solve for 0<x<2
7sin2x-11 = 4sin2x-13
7sin2x-11-4sin2x+13=0
sin2x = -2/3

How can I solve it further, giving the answer in exact form?
(Thinking)(Thinking)

• Jan 1st 2013, 01:51 PM
zachd77
Re: Trig Equations
Quote:

Originally Posted by xoxo
Solve for 0<x<2
7sin2x-11 = 4sin2x-13
7sin2x-11-4sin2x+13=0
sin2x = -2/3

How can I solve it further, giving the answer in exact form?
(Thinking)(Thinking)

Do you mean you are solving on the interval Attachment 26442?
• Jan 1st 2013, 02:14 PM
xoxo
Re: Trig Equations
yes
• Jan 1st 2013, 03:04 PM
zachd77
Re: Trig Equations
Your equation has a function of 2x. Therefore, we need to expand the interval that you are solving for, because when you take the arcsin of both sides, you must account for the 2x, not just x. So, we expand our interval from 0<x<2(pi) to 0<2x<4(pi).
When we take the arcsin of both sides, you will need to find all of the solutions that exist in (0,4pi). Then, when you have all solutions for 2x, just divide by two FOR ALL SOLUTIONS, and then you will have your needed solutions (I'd assume that there will be four solutions).