Kako pretvorim r = 3 + 3sec (theta) v kartezično enačbo?

Odgovor:

# x ^ 2 + y ^ 2 = (9x ^ 2) / (x-3) ^ 2 #

Pojasnilo:

Večkrat vse izraze # rcostheta #, od # costheta * sectheta = 1 #

# r ^ 2costheta = 3rcostheta + 3r #

# rcostheta = x #

# r = sqrt (x ^ 2 + y ^ 2) #

#xsqrt (x ^ 2 + y ^ 2) = 3x + 3sqrt (x ^ 2 + y ^ 2) #

#sqrt (x ^ 2 + y ^ 2) (x-3) = 3x #

#sqrt (x ^ 2 + y ^ 2) = (3x) / (x-3) #

# x ^ 2 + y ^ 2 = (9x ^ 2) / (x-3) ^ 2 #

Poišči vrednost theta, če, Cos (theta) / 1 - sin (theta) + cos (theta) / 1 + sin (theta) = 4?

Theta = pi / 3 ali 60 ^ @ OK. Dobili smo: costheta / (1-sintheta) + costheta / (1 + sintheta) = 4 Zdaj ignoriramo RHS. costheta / (1-sintheta) + costheta / (1 + sintheta) (costheta (1 + sintheta) + costheta (1-sintheta)) / ((1-sintheta) (1 + sintheta)) (costheta ((1-sintheta) ) + (1 + sinteta)) / (1-sin ^ 2theta) (costheta (1-sintheta + 1 + sintheta)) / (1-sin ^ 2theta) (2costheta) / (1-sin ^ 2theta) Pitagorejska identiteta, sin ^ 2teta + cos ^ 2tea = 1. Torej: cos ^ 2theta = 1-sin ^ 2theta Zdaj, ko vemo, da lahko, pišemo: (2costheta) / cos ^ 2theta 2 / costheta = 4 costheta / 2 = 1/4 costheta = 1/2 theta = cos ^ - 1 (1/2)

Kako prepišem naslednjo polarno enačbo kot enakovredno kartezijsko enačbo: r = 5 / (sin (theta) -2cos (theta))?

Y = 2x + 5 r = 5 / (sin (theta) -2cos (theta)) r (sin (theta) -2cos (theta)) = 5 rsin (theta) -2rcos (theta) = 5 Sedaj uporabljamo naslednje enačbe: x = rcostheta y = rsintheta Dobiti: y-2x = 5 y = 2x + 5

Pokažite, da (1 + cos theta + i * sin theta) ^ n + (1 + cos theta - i * sin theta) ^ n = 2 ^ (n + 1) * (cos theta / 2) ^ n * cos ( n * theta / 2)?

Glej spodaj. Naj bo 1 + costheta + isintheta = r (cosalpha + isinalpha), tukaj r = sqrt ((1 + costheta) ^ 2 + sin ^ 2theta) = sqrt (2 + 2costheta) = sqrt (2 + 4cos ^ 2 (theta / 2) ) -2) = 2cos (theta / 2) in tanalpha = sintheta / (1 + costheta) == (2sin (theta / 2) cos (theta / 2)) / (2cos ^ 2 (theta / 2)) = tan (theta / 2) ali alfa = theta / 2, nato 1 + costheta-isintheta = r (cos (-alpha) + isin (-alpha)) = r (cosalpha-isinalpha) in lahko napišemo (1 + costheta + isintheta) ^ n + (1 + costheta-isintheta) ^ n z uporabo DE MOivrejevega izreka kot r ^ n (cosnalpha + isinnalpha + cosnalpha-isinnalpha) = 2r ^ ncosnalpha = 2 *