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数学 高校生

写真の解説の、5.6行目がわかりません。 どうして「CD⊥l」なら「角BCDは2平面α、βのなす角に等しい」のですか? 解説お願いします🙏🏻💦

3 わ 508 例題 300 2 平面のなす角と三角比 思考プロセス βのなす角が30° であるとする。 α と 2 平面 α, βの交線上に点Aを, α上に点Bを直線AB と交線のなす角が60° となるようにとる。 また, B から交線に下ろした垂線を BC, B から βに下ろした垂線をBD とする。 ∠BAD = 0 とするとき, tan0の値を求めよ。 α, βのなす角は30° であるが, 0は30° ではない。 逆向きに考える ①条件 条件 ③ tan を求める [⊥BC 11 △□を考える 解 AB=α とおく。 △ABCについて ∠ACB=90°, ∠BAC = 60° より a AC = -1/12/AB=1/27 例題したがって 115| √3 1/12/BC-10 -BC = BD = a 4 △ADB において, 三平方の定理により AD=√AB-BD2 a² tan O BD より, ADとBD を求める △□を考える AD Action》 交線に垂直な各平面上の2直線のなす角は, 2平面のなす角を使え C でBCとのなす角が30°△□を考える √3 BC=√3AC = 2 BD ⊥ β, BC 1 であるから, 三垂線の定理により CD 1 よって, ∠BCD は 2 平面 α, βのなす角に等しいから ∠BCD = 30° ゆえに,直角三角形 BCD に注目すると = A 60° √√3 4 BD √√3 √13 AD 4 4 a÷ B ~30° /13 4 a = C 60° √39 13 A 練習 300 2 平面 α, βのなす角が60° であるとする。 α と βの交線上に点Aをとり, α上に点Bを直線 AB と交線lのなす角が45°, β上に点Cを直線 AC と交線lのなす角が45° となるようにとる。 Bから交線に下ろした垂線をBD とすると, C から交線に下ろした垂線が CD となるとき, COS ∠BAC の値を求めよ。 a fact ・A ~30° 直角三角形ABCの3辺 の長さの比は AC:AB:BC=1:2:√3 BD 1 β より BDZ また, BC ⊥l であるから 平面 BDC よって CD l としてもよい。 A ★★ BD I β であるから, BD は β上のすべての直線に 垂直である。 --------Q 10 45% D AD 45° B √√3 D B Ta a p.512 問題300 四面体O 火のこと (1) 0 (2) OC のプロセス (1) Al 目 2直 (1) Act

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数学 高校生

英語の長文ってどうやったら読めるようになりますか

1 次の英文を読んで、問 (1) ~ (5) に且本語で答えなさい。 Lobola is the African custom of paying fora bride. Although it is an old custom, not In fact, it is being debated in Botswana. everyone in African cultures is happy with it. Many people, including many women, support payment of lobola. They explain that in Tswana culture, a marriage means joining a family, not just marrying an individual. The idea of marrying into a family is very African. just the man.Through marriage, the young woman's family loses their daughter as she then becomes a part of her husband's family. Lobola is a way to show thanks. It is a form of generosity in African culture. In its traditional form, they also explain, the groom's family gave cattle to the bride's family. But it didn't matter whether the family owned cattle or not. A woman does not get married to A man only had to pay what he could afford if he had no cattle, he could give something else, even the smallest form of payment. The tradition of lobola was a matter of pride. Today, lobola is often given in cash. purchase of a bride. Lobola is meant to join two families together. They know that But its supporters say it is not about the some people abuse the custom. But they believe that the tradition should not be tossed out because it has many positive effects. Rather than get rid of it, many believe it should just be explained better. However, many others say this custom should be stopped. They think it has become commercialized. Families make lots of demands on the groom. They think this makes lobola look very bad. They argue that in Africa's past, a girl was an asset at home. and other household chores. She did the cooking When a family lost that child through marriage, it demanded payment. Today, they think that lobola has changed into a useless tradition. In this custom, a man is buying the right to control a woman. They say women are individuals with rights. In today's world, parents do not have to be paid for a bride because their male and female children are equal. They all work and make contributions to the household. They believe that paying lobola makes it seem like a man is buying a pair of shoes or a bicycle, instead of getting married. They also argue that it is often a financial burden for couples. It is too difficult for many people to pay the price asked. So, is lobola a rich tradition, bringing families together? Or is it an ugly custom of buying women? This debate continues in Botswana, as does the custom.

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