I am reading some fairly dense engineering material and just trying to
follow some of the mathematics. If I remembered all of my
exponentials and integration rules, this wouldn't be a problem :) I
broke my problems reading the material in to the following two
questions. Bonus question answers would be appreciated, but are
unnecessary.
1. Please show the step(s) that reduce
SQRT(2*E/T)
* INTEGRAL[Bounds:0,T][COS(2*pi*f_0*t+theta) * EXP(j*2*pi*f*t) dt]
to
SQRT(T*E/2)
* [{SIN[pi*T*(f-f_0)]/[pi*(f-f_0)]} + {SIN[pi*T*(f+f_0)]/[pi*(f+f_0)]}]
* EXP(-j*pi*f*T) * EXP(-j*theta)
2. Similarly, please show the step(s) that reduce
INTEGRAL[Bounds:0,2T][ SIN(pi*t/2/T) * EXP(-j*2*pi*f*t) dt]
to
(4*T/pi)
* COS(2*pi*T*f) / (1-16*T^2*f^2)
* EXP(-j*2*pi*f*t)
I have a note that this is supposedly "easily done" using the trig
identity SIN(x) = [ EXP(jx) - EXP(-jx) ] / 2
:)
BONUS #1 (Good for a big tip): Please show the steps that reduce
[ (T/2) * [ SIN(pi*f*T/2) / (pi*f*T/2) ] * EXP(-j*2*pi*f* T/2) ] -
[ (T/2) * [ SIN(pi*f*T/2) / (pi*f*T/2) ] * EXP(-j*2*pi*f*3T/4) ]
to
(T/2) * [SIN(pi*f*T/2)/(pi*f*T/2)] * EXP(-j*pi*f*T) * [2*j*SIN(pi*f*T/2)]
BONUS #2 (Good for a bigger tip, if bonus #1 is answered): Please show
why EXP(-j*pi*f*T)^2 = 1. I'm not sure if this is true, but when I
read through a couple proofs, this seems to hold. |