 Isolate to solve the equation - XP Math - Forums Sign Up FREE! | Sign In | Classroom Setup | Common Core Alignment  XP Math - Forums Isolate to solve the equation 04-02-2010 #1 magmagod   Join Date: Mar 2010 Posts: 9 Isolate to solve the equation So the question is basically solve each equation for 0 04-03-2010   #2
MAS1   Join Date: Dec 2008
Posts: 249 Quote:
 Originally Posted by magmagod So the question is basically solve each equation for 0
Wow, these are tough problems the way you have presented them. Maybe you have left out some parentheses or something.

For the 1st one, I am assuming that first dash is NOT a negative sign, therefore:
sinx*sqrt(2) = 2sinxcosx
sqrt(2) = 2cosx
sqrt(2)/2 = cosx
Taking the inverse cos of both sides gives
x = pi/4 and 7*pi/4

If the first dash is a negative sign, then x = 3*pi/4 and 5*pi/4.

Your solution is incorrect because 2sinxcosx = sin2x, not 2sinx.   04-04-2010   #3
MAS1   Join Date: Dec 2008
Posts: 249 Quote:
 Originally Posted by MAS1 Wow, these are tough problems the way you have presented them. Maybe you have left out some parentheses or something. For the 1st one, I am assuming that first dash is NOT a negative sign, therefore: sinx*sqrt(2) = 2sinxcosx sqrt(2) = 2cosx sqrt(2)/2 = cosx Taking the inverse cos of both sides gives x = pi/4 and 7*pi/4 If the first dash is a negative sign, then x = 3*pi/4 and 5*pi/4. Your solution is incorrect because 2sinxcosx = sin2x, not 2sinx.
I see you edited your equations.

For the second one:
2cosx - 3/cosx + 2*sqrt(2) = 0
cosx*[2cosx - 3/cosx + 2*sqrt(2)] = cosx*0
2(cosx)(cosx) + 2sqrt(2)*cosx - 3 = 0
Using quadratic formula to solve for cosx gives:
cosx = sqrt(2)/2 and cosx = -3*sqrt(2)/2
For the 1st solution x = pi/4 and 7*pi/4
For the 2nd solution x = arccos(-3*sqrt(2)/2)

Sorry, I don't have a calculator with trig functions on it for the second solution.

MAS1   04-05-2010 #4 jmw106462      Join Date: Feb 2010 Posts: 388 sinx*sqrt(2 = 2sinxcosx sqrt(2 = 2cosx sqrt(2/2 = cosx x = pi/4 and 7*pi/4 This is what the answer is very hard like mas1 said. Mostly the way you presented them, didn't queit get the problem at first. Hope you do well, good luck! __________________ Please refrain from sending me frivolous PM's  Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
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