I beg all of you to pls help me to solve this trigonometric identities equation..the problems are 10, i already solve 5 and obviously, there's a remaining 5 problems..I can't solve them i mean i've been solving those remaining 5 questions for 5 hours and still no success..pls help me...these are the questions...

* those enclosed in parentheses indicated that the number inside is an exponent)

* / = over e.g. cosx/sinx (cosx over sinx)

1.) cos(4)x - sin(4)x = 2cos(2)x - 1

2.) 1 - (sinx / cscx) = cosx / secx

3.) tan x / (1 - tan(2)x) = cosx / (cscx - 2sinx)

4.) secx sinx / (tanx +cotx) = sin(2)x

5.) cos(2)x - sin(2)x = 1 - 2sin(2)x

plss help me...thank you in advance for those who'll helped...

Godbless you all!!!