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数学 高校生

面積の方なのですが、積分範囲は、0から√eの x^2/2e-logxではいけないのはなぜですか。なぜそのような解き方をしているのでしょうか。

解答 00000 基本 例題 179 接する2曲線と面積 曲線 y=logx が曲線 y=ax2と接するように正の定数αの値を定めよ。 また, そのとき,これらの曲線と x軸で囲まれる図形の面積を求めよ。 [信州大」 基本 85 176 17 指針(前半)2曲線y=f(x), y=g(x) が点 (b,g) で接する条件は y=f(x)) |f(p)=g(p) y 座標が一致 共通接線 |f'(p)=g'(p) 傾きが等しい y=g(x) 接する (p.147 基本例題 85 参照。) (後半)(前半)の結果から2曲線の接点の座標がわかるか ら,グラフをもとに2曲線の上下関係をつかみ、面積を 計算。 なお,面積の計算には [1] x 軸方向の定積分 P [2] y 軸方向の定積分 の2通りが考えられるが,ここでは [1] の方針で解答してみよう。 f(x)=logx, g(x) =ax2 とすると f'(x)=1/12g'(x)=2ax 2曲線 y=f(x), y=g(x) がx=cの点で接するための条件 logc=ac² は ① かつ =2ac C ②から a= (3 2c2 <①:f(c)=g(c) ②:f'(c)=g'(c) ③①に代入して logc= 2 ゆえに =√e したがって a= このとき、接点の座標は よって, 求める面積Sは (√e, 1/1) s=S/xdx-Slogxdx = Do 2e -[4-[logx-x]" 2e XC = 1/1√e-(1√e-√e+1) -√√-1 12 S 1 2c2 = /y=logx 12 2e 1 y= 2e √e x² x (後半) の別解 (指針の [2] による) y= ±±±±x² (x≥0) 2e ⇔x=√2e y=logx⇔x=eカ s=$(e-√zey) = [e³ 2√2 y√y] 3 2√2e 1 =√e- 3 2 3 1-2 |

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英語 高校生

英語長文問題です (1)イ?ウ? (2)ウ (3)イ (4)ア 解いてみたのですが(1)が分かりませんでした (2)(3)(4)もあっていますか?

14 Paraphrase Rapid Reading [速読 目標解答時間12分 ] 鶴と亀の物語から得られる教訓は何でしょうか。 Listening EX ON の 船 1 Once there were two cranes and a tortoise who lived by a lake and became good friends. They played together all day long, sunning themselves on the sand and swimming in the lake. They were very happy and wanted to be together forever. 2 But that year there was a drought*. For five months, no rain fell at all. The rivers and the land cracked. Each day, the little lake where the tortoise and cranes dried up, lived became smaller and smaller. 3 One day the two cranes flew into the air to see how things were, and came back in the evening saying, "Tortoise, everyone is moving to the Heavenly Lake. I think we should move too. If we stay here, we'll die of hunger and thirst." 13 end sky gra 14 to O P 1 5 The tortoise shut his little eyes and cried. "Oh, you can fly or hurry as fast as you 10 get to the Heavenly Lake. But I can neither fly nor walk fast. Within three days I will be nothing but an empty shell! We have been friends for so long. Please don't leave want, and me behind." 5 The tortoise cried so much that the cranes, unable to hold their own tears back, did not have the heart to leave him behind. So they decided to stay at the lake with the 15 tortoise for a while. Perhaps the rain would come in a few days. 6 But the weather did not change. Clear stars dotted the sky at night, and the sun was they thought hot and cruel el by day. The little lake was nearly dry. The cranes said again they must go. The tortoise knew that he could not keep them there any longer, so he pleaded* with them, saying "We have been friends for so long! Can't you think of a way to 20 take me along?" 7 They thought long and hard. After some time the cranes said, "Tortoise, we have a plan, but it will be difficult." 18 The tortoise asked eagerly, "What is it? What is it?" "We'll hold two ends of a stick in our beaks*, and you can hold on to the middle with 25 your mouth. Then we can fly, carrying you between us. What do you think of the idea?” 10 The tortoise was so happy that he nearly jumped. "Yes, yes! That's a good idea! Let's start at once!" 11 The cranes were very happy, too, but they had to give him a warning. "You must be NOTES drought : 干ばつ plead : 嘆願する 32 UNIT 8 beak (鳥の) くちばし )( ).no パート ごとの 音声 ON

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