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Mathematics Senior High

なんのために最後に漸近線を求めているのですか?

重要 例題 78 z を 0 でない複素数とし,x,yをz+ 1 2 =x+yi を満たす実数,αを0<a</ を満たす定数とする。z が偏角 αの複素数全体を動くとき、xy平面上の点 (x, y) の軌跡を求めよ。 *U*2301 [類 京都大] 重要 26 解答 指針偏角αの範囲が条件であるから、極形式z=r (cosatisina) (0) を利用。 ■iの形に表すことにより,x,yをそれぞれr, aで表す。 12+- 2 つなぎの文字を消去 して,x,yだけの関係式を導く。なお、>0や0<a< より, xの値の範囲に制限がつくことに注意。 ゆえに TOADE z=r(cosatisina) (x>0,0<a</1/2)とすると ゆえに 0<a</であるから よって r+ cos a' - 1 (cosa + sina) == ² ( cos x r= 2 COS r 2 -=1から 練習 ③78 1 z+ -=r(cosa+isina)+¹(cosa-isina) 2 * = = =(r+ + )cosa+i(r— — )sina cosa, y=(r-1) sina x=(x+1/27) 1 x 2 cos a x² Acos2a 双曲線 w=z+. =r+ r a² cos a よって x≧2cosa また, >0 から ゆえに したがって 求める軌跡は osax + cos a>0, sin a>0 y sina y 表す図形 (2) r sin a したがって 4sin² a ここで, >0であるから, (相加平均) (相乗平均) により x²y² COS α -(tana)x<y<(tana)x 4 cos' a 4sin'α ;-). - / - ( 1 x =2 2. 等号はr=1のとき成り立つ。 _____________> +___>0, sina sin a COS α sina sina)=1 COS α COS α 63401 -=1のx≧2cosα の部分 < 絶対値や偏角αの範囲 に注意。 1 2 =-{cos(-a)+isin(-a)} ◄2+1/2=x z+ =x+yi 検討 第4章で学ぶ極 限の知識を用いて, y が実数 値全体をとりうることを調べ ることもできる。 lim m(x-¹)=∞, に lim (-1)=-∞であり, sinα> 0から lim y=-∞, limy = ∞ r+0_ →0 点 (x, y) の軌跡は次の図の 部分。 (0) y=(tana)x を求めている -2cosa / 2cosa y=-(tana)x 0 でない複素数zが次の等式を満たしながら変化するとき, 点z+-が複素数平 面上で描く図形の概形をかけ。 (1) |2|=3-(2) |z−1|=|z-i| 139 2章 10 媒介変数表示

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English Senior High

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4 20 科学 420 words Chapter 1 The recipe for making any creature is written in its DNA. So last year, when 1-1 geneticists* published the near-complete DNA sequence of the long-extinct woolly mammoth, there was much speculation about whether we could bring this giant creature back to life. 5 東京理科大学 Creating a living, breathing creature from a genome* sequence that exists only in a computer's memory is not possible right now. But someone someday is sure to try it, predicts Stephan Schuster, a molecular biologist at Pennsylvania State University and a driving force behind the mammoth genome project. So besides the mammoth, what other extinct beasts might we bring back to life? Well, 12 10 it is only going to be possible with creatures for which we can recover a complete genome Without one, there is no chance. And usually when a creature dies, the (1) - DNA in any flesh left untouched is soon destroyed as it is attacked by sunshine and bacteria. sequence. There are, however, some circumstances in which DNA can be preserved. If your 15 specimen froze to death in an icy wasteland such as Siberia, or died in a dark cave or a really dry region, for instance, then the probability of finding some intact stretches of DNA is much higher. Even in ideal conditions, though, no genetic information is likely to survive more than a million years. - so dinosaurs are out and only much younger remains are likely to yield good-quality DNA. "It's really only worth studying specimens that are less than 100,000 years old," says Schuster. The genomes of several extinct species besides the mammoth are already being sequenced, but turning these into living creatures will not be easy. "It's hard to say that something will never ever be possible," says Svante Pääbo of the Max Planck Institute 25 for Evolutionary Anthropology in Germany, "but it would require technologies so far removed from what we currently have that I cannot imagine how it would be done." But then (3) 50 years ago, who would have believed we would now be able to read the instructions for making humans, fix inherited diseases, clone mammals and be close to creating artificial life? Assuming that we will develop the necessary technology, we have 30 selected ten extinct creatures that might one day be resurrected. Our choice is based not just on practicality, but also on each animal's "charisma" - just how exciting the prospect of resurrecting these animals is. 1-3

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