Those are not actual errors, but warnings. They are there because you are trying to divide something by zero.
Namely, you are setting M[0] = 0 and then dividing by M[0] (at first iteration, where m = 0) and same for P[0].
The question is, what do you want the first values to be?
Maybe a solution would be initialize the zero values as you wish (before the loop) and start the loop with m=1 (so using for m in range(1,n+1):). Is that what you needed?
However, the warning may still be there if at different iterations P[m] or M[m] will be zero.
T_max = 0.5 * v_PM(Me) * RTOD
DT = (90 - T_max) - np.fix(90 - T_max)
n = int(T_max * 2)
P = np.zeros((n+1))
T = np.zeros((n+1))
M = np.zeros((n+1))
RR = np.zeros((n+1))
LR = np.zeros((n+1))
SL = np.zeros((n+1))
# initialize your values
M[0] = 0 # actually not needed
P[0] = 0 # actually not needed
RR[0] = 0 # actually not needed
LR[0] = 0 # actually not needed
SL[0] = 0 # actually not needed
T[m] = (DT) * DTOR
for m in range(1,n+1):
T[m] = (DT + m) * DTOR
#Mach from T[i] using T[i] = v_PM (FALSE POSITION)
func = lambda x: T[m] - v_PM(x)
M[m] = brentq(func, 1, Me+1)
P[m] = TR * np.tan(T[m]) #X-AXIS POINTS
#RR SLOPES
RR[m] = -TR / P[m]
#LR slopes
LR[m] = (np.tan(T[m] + np.arcsin(1 / M[m])))
SL[m] = -RR[m]
