Question

I am pretty confused fourier series. In this question, it said bn= f(x)cos(npix/3)dx, but what I learned is this formula should be bn= f(x)sin(...)dx. Can you help me explain why in this sheet bn=f(x)cos(npix/3)dx instead of bn= f(x)sin(...)dx? Thanks!

SVT) 44fís) = Tegg (SD54) > [s): seg / 40) f()24l on (0, 3) Tkn . Extend it to sin fems in the Linde k extension is evin all i feurs ey expansion arc zelo. f(x). Z bn cos Chrox) Ang bns fix) eslnax) dx - 2 L éxt) (ny) dx - 4 l G5n,x)dx + 4 Sasingx) dx - 4 ( X sia ly) - 2 Si lagx) dx) | 4 ( 6 3 stk na) 3 - 0 - LE SYML)? J) - 4 G)2 (ces (re.) Cos())2)' (61)" - 1) 12 (0"-) Wien n70. |