Grade

Type of questions

Mathematics Senior High

285番の解答の赤線部について、点Hの極座標が(1,π/3)というところからなぜ突然極方程式が求められるのかがわかりません。どのような過程があるのでしょうか

B問題 285 (1) * 点A(2,0)を通り, 始線とのなす角が 5 極座標に関して,次の直線の極方程式を求めよ。 (4) ①をx2+y2-4x=0 に代入すると recos20 +12sin204rcos0=0 すなわち よって (cos20 + sin20)-4rcos0= 0 rr-4cos0)=0 したがって r = 0 または r=4cose = 0 は極を表す。 また, r=4cose は極座標が (20) である点を中心とし, 半径2の円を表 す。 これは極を通る。 よって, 求める極方程式は r=4cose 別解 (4) 方程式を変形すると (x−2)2+y2=4 この方程式が表す円の半径は2で,中心の極座 標は (2,0)である。 よって, 求める極方程式は r=4cos0 283 曲線上の点P(r, 0) の直交座標を(x, y) とす ると rcos0=x, rsin0=y, r2=x2+y2 ...... (1) 極方程式v=cos0+sin0 の両辺にrを掛け ると r2=rcos0+sin 0 ) すなわち re=rcos0+rsin0 これに.① を代入して1, 0 を消去すると x2+y2=x+y x2+y²-x-y=0 よって 参考 +nz 曲線r= cos0 + sin0は極 (01/27) (nは整数) を通るから, y = cos0+sin の両辺 にを掛けても同値である。 (2) cos20 = cos20 sin' 0 から y2(cos20-sin20)=-1 すなわち (rcos0)-(rsin0)=-1 これに ① を代入して, 0 を消去すると x²-y²=-1 ↑ の直線 したがって 4(x2+y^2)=x2+6x+9 284 放物線上の点P の極座標を(r, 0) と し, Pから準線ℓに 下ろした垂線を PH とすると Y= 285 (1) 極0からこの 直線に下ろした垂線を OH とする。 右の図か ∠AOH= 3x²+4y²-6x-9=0 OP= PH ここで, OP=r, PH=3-rcos であるから r=3-rcos 8 よって, 求める放物線の極方程式は 3 1+ cos 20 2 IC 3 TC 6 解答編 = O 0 (2) 極0からこの直線に 下ろした垂線を OH, 直線と始線の交点を P OH-OAcos-2.1/28-1 =1 よって, 点Hの極座標は 1, したがって、求める極方程式は rcos (0-3)=1 B(1.4) H A l -69 X

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English Junior High

この問題の(4)なのですが、 I will try anything faster than any other student in my class. どんなことも他の人(クラスメート)よりも早く挑戦する と解答したのですが、あっていますか? 添削お願いします。

19 ハルナ(Haruna) がヒューズ先生 (Mr. Hughes) と話をしています。この対話文を読んで、 [1]~[(3) に入る最も適当なものをそれぞれあとのア~エのうちから一つずつ選び、その 符号を書きなさい。 また、対話文の内容に合うように、 (4) に入る言葉を英語で書きなさい。 ただし、語の数 は10語程度(.?! などの符号は語数に含まない。) とすること。 Haruna Mr. Hughes, do you have time ? Mr. Hughes Of course. Do you have any questions? Haruna:Yes, at the end of the class, you said, "Be the first penguin." (1) Mr. Hughes: All right. You know penguins, right? Penguins are birds that cannot fly but car swim in the sea. Haruna Yes, of course. I have seen them in an aquarium. Mr. Hughes : Some people say that there is no leader in the world of penguins but that is not true. When they catch food or run away to a safe place, one penguin moves first, and then the rest of them (2) Haruna Mr. Hughes: Wow, that's very interesting. For example, (3) | to jump into the sea to catch food because there is sometimes danger in the sea. But when one brave penguin jumps into the sea, all 0000/r

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TOEIC・English Undergraduate

わからないので答えを教えてもらいたいです。

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