differentiate this! (1 Viewer)

[viraj30]

can someone please find the second derivative of 2sin^2x - 2sinx - 1.....i keep getting different answer than the tb..i got 4cos2x + 2sinx..thnks

 

[Internet_Police]

y= 2 (sin(x))^2 -2sin(x)-1

dy/dx= 2*2 (sin(x))^1 cos(x) -2cos(x)

dy/dx= 2 * 2sin(x)cos(x) -2cos(x) = 2sin(2x) -2cos(x) //by double angle formula

d^2y/ dx^2 = 4cos(2x) +2sin(x)

The text probably did not simplify the 4sin(x)cos(x) , they probably did a product rule on it. Their answer probably looks different but it is still equivalent.

 

[viraj30]

check pg 168 11(b) of fundamental mathematics (terry)(dunno if there are different editions)..it says y''= -2sinx-4cos2x..so it means that its wrong yeh?? god this book's filled with mistakes

EDIT- and i dont even get q14 of ex4.6...i thought the gutter's shape was 3d so it must have a length to find its surface area...but u only had to find the cross section area n they didnt mention it in the question...so confusing

 

[kfnmpah]

wolframalpha.com
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