14/09/07 16:23:22.96 s0pjH4z5
(2r-rsinθ)^2＋(rcosθ)^2
=4r^2 -4r^2 *sinθ +r^2 *(sinθ)^2 + r^2 *(cosθ)^2
(sinθ)^2 + (cosθ)^2 = 1より
与式 = 4r^2 -4r^2 *sinθ +r^2 *((sinθ)^2 + (cosθ)^2)
= 4r^2 -4r^2 *sinθ +r^2
= 5r^2 - 4r^2 *sinθ
∴r*sqrt(5- 4sinθ)
14/09/07 16:23:22.96 s0pjH4z5
(2r-rsinθ)^2＋(rcosθ)^2
=4r^2 -4r^2 *sinθ +r^2 *(sinθ)^2 + r^2 *(cosθ)^2
(sinθ)^2 + (cosθ)^2 = 1より
与式 = 4r^2 -4r^2 *sinθ +r^2 *((sinθ)^2 + (cosθ)^2)
= 4r^2 -4r^2 *sinθ +r^2
= 5r^2 - 4r^2 *sinθ
∴r*sqrt(5- 4sinθ)