Com es divideixen (i + 3) / (-3i +7) en forma trigonomètrica?

Com es divideixen (i + 3) / (-3i +7) en forma trigonomètrica?
Anonim

Resposta:

# 0.311 + 0.275i #

Explicació:

Primer reescric les expressions en forma de # a + bi #

# (3 + i) / (7-3i) #

Per a un nombre complex # z = a + bi #, # z = r (costheta + isintheta) #, on:

  • # r = sqrt (a ^ 2 + b ^ 2) #
  • # theta = tan ^ -1 (b / a) #

Anem a cridar # 3 + i # # z_1 # i # 7-3i # # z_2 #.

Per # z_1 #:

# z_1 = r_1 (costheta_1 + isintheta_1) #

# r_1 = sqrt (3 ^ 2 + 1 ^ 2) = sqrt (9 + 1) = sqrt (10) #

# theta_1 = tan ^ -1 (1/3) = 0,32 ^ c

# z_1 = sqrt (10) (cos (0.32) + isin (0.32)) #

Per # z_2 #:

# z_2 = r_2 (costheta_2 + isintheta_2) #

# r_2 = sqrt (7 ^ 2 + (- 3) ^ 2) = sqrt (58) #

# theta_2 = tan ^ -1 (-3/7) = - 0,40 ^ c #

No obstant això, des de llavors # 7-3i # és en el quadrant 4, hem d’obtenir un angle positiu equivalent (l’angle negatiu s’acosta a les agulles del rellotge al voltant del cercle i necessitem un angle antihorari).

Per obtenir un angle positiu equivalent, afegim # 2pi #, # tan ^ -1 (-3/7) + 2pi = 5.88 ^ c #

# z_2 = sqrt (58) (cos (5.88) + isin (5.88)) #

Per # z_1 / z_2 #:

# z_1 / z_2 = r_1 / r_2 (cos (theta_1-theta_2) + isin (theta_1-theta_2)) #

#color (blanc) (z_1 / z_2) = sqrt (10) / sqrt (58) (cos tan ^ -1 (1/3) - (tan ^ -1 (-3/7) + 2pi) + isin tan ^ -1 (1/3) - (tan ^ -1 (-3/7) + 2pi) #

#color (blanc) (z_1 / z_2) = sqrt (145) / 29 (cos tan ^ -1 (1/3) -tan ^ -1 (-3/7) -2pi + isin tan ^ -1 (1/3) -tan ^ -1 (-3/7) -2pi) #

#color (blanc) (z_1 / z_2) = sqrt (145) / 29 (cos (-5,56) + isin (-5,56)) #

#color (blanc) (z_1 / z_2) = sqrt (145) / 29cos (-5,56) + isqrt (145) / 29sin (-5,56) #

#color (blanc) (z_1 / z_2) = 0.311 + 0.275i #

Prova:

# (3 + i) / (7-3i) * (7 + 3i) / (7 + 3i) = ((3 + i) (7 + 3i)) / ((7-3i) (7 + 3i)) = (21 + 7i + 9i + 3i ^ 2) / (49 + 21i-21i-9i ^ 2) = (21 + 16i + 3i ^ 2) / (49-9i ^ 2) #

# i ^ 2 = -1 #

# = (21 + 16i-3) / (49 + 9) = (18 + 16i) /58=9/29+8/29i~~0.310+0.275i#