trigonometric equations

[Dannyk]

Please help me!!I need some solves for next equations
1)sin⁴ +cos⁴x=7/2sinx*cosx
2)sin3x+cos2x=1
3)cos4x*cos5x=cos6x*cos7x

 

[Dannyk]

WHY do you need "some solves"?
Can you show your work so far...we "check", no "do".

i don't understand this equation and i need help

 

[Ishuda]

Please help me!!I need some solves for next equations
1)sin⁴ +cos⁴x=7/2sinx*cosx
2)sin3x+cos2x=1
3)cos4x*cos5x=cos6x*cos7x

You will have to 'play around' with the trig identities to find the x which is the solution for the equations. What have you done so far? Please show us your work so we may know how to help. You should also read
http://www.freemathhelp.com/forum/threads/77972-Read-Before-Posting!!

As a hint for the first one, suppose you were to use the trig identities
2 sin(x) cos(x) = sin(2x)
cos²(x) = \(\displaystyle \frac{1+cos(2x)}{2}\)
sin²(x) = \(\displaystyle \frac{1-cos(2x)}{2}\)
and
cos²(2x) + sin²(2x) = 1