ตอบ:
# R ^ 2 = 4 / (cos ^ 2theta + 4sin ^ 2theta) #
# r = sqrt (4 / (cos ^ 2theta + 4sin ^ 2theta)) = 2 / sqrt (cos ^ 2theta + 4sin ^ 2theta) #
คำอธิบาย:
เราจะใช้สองสูตรนี้:
# x = rcostheta #
# การ y = rsintheta #
# x ^ 2 r = ^ ^ 2cos 2theta #
# Y ^ 2 r = ^ ^ 2sin 2theta #
# R ^ ^ 2cos 2theta + 4r ^ ^ 2sin 2theta = 4 #
# R ^ 2 (cos ^ 2theta + 4sin ^ 2theta) = 4 #
# R ^ 2 = 4 / (cos ^ 2theta + 4sin ^ 2theta) #
# r = sqrt (4 / (cos ^ 2theta + 4sin ^ 2theta)) = 2 / sqrt (cos ^ 2theta + 4sin ^ 2theta) #
