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数学 高校生

不等号の下に=がどういう時に付くのかがよくわかりません

例題129 三角関数 0≦0 <2のとき、次の不等式を解け. (1) 2 sin 02-1 (8 (2) 2 cos > IS 解答 (1) 2sin≧-1 より, sin0= - 考え方 三角関数を含む不等式は,まず「=(イコール)」とおいて,方程式を解くとよい あとは、例題128 (p.253) と同様に考える. ここでは単位円を用いて考えてみる =! よって、 右の図より、 7 11 osos, r≤0<2n <2π 6 (3) tan0≥-√3 5 より、0, (2) 2 cos >√3 h, cos 0>. √√3 cos0= より 2 よって、 右の図より sin 02 11 17/11/1/2π TC 6 6 11 0≤0<n<0<2n 6' л≤0<2n √3 2 11 -π 匹 6'6 7.11 tan0=-√3より.8=12/21. 1/23 5 よって、 右の図より 37 π 2 2' 3 1 2 9 17 15 3 (3) tan O -1 T 11 6 例題129 をグラフで考えると次のようになる. (1) YA (2) YA y=sine /color] 「53 -1 -√3- 1 O .7 6 π 6、 -TC TC y=coso 12 0 ale=0.4 √√3 2 1x 12 上 x AX x **** -√3 「まず 「=」とおいて入 程式を解く. 直線y=-12 より上り 0≦0.2より、2を 含まないことに注意す る. まず「=」とおいて 程式を解く. 0キ 直線x= 11 1/7<0</20 <θ< √3 しない まず「=」とおいて 程式を解く. 傾きが-√3よりも大 きい. (3) YA T 3 三角関数を含む不等式は、 まず 「=(イコール)」 とおいて、方程 式を解くの増加に伴い, sin 0, cos 0, tan 0 の値はどのよう に変化するか単位円を用いて考える Bo 回単 2'2" に注意する. より πであること by=tand F

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英語 高校生

下から5行目のit would~の文構造がわからないです。back upはどのような働きをしているのでしょうか。 教えて頂けるとありがたいです。

A Makeover for Hoover Dam Hydropower has attracted increasing attention in recent years as a renewable type of clean energy. As long as a suitable water source is available, hydropower facilities are usually good investments, producing energy in a manner that generates far less air pollution and CO2 emissions than fossil fuels do. The most common way to generate hydropower is to trap water at a high elevation behind a dam so it can be released and used to spin turbines below, which, in turn, power electricity-producing generators. However, hydropower has its drawbacks. Droughts and increased water consumption have reduced the flow of many rivers. As rivers become shallower, the necessary volume of water for electricity difficult to maintain, and power supply and generation is dependability are negatively impacted. more Variability in water levels has particularly affected Hoover Dam, a mega-scale hydropower facility in the US state of Nevada. Built in the 1930s at enormous expense to control the frequently flooding Colorado River and maintain a water supply for farmland irrigation, the dam's hydropower capabilities were seen as a way to recover some of the costs of its construction over the long term. The dam's electricity-generating capacity, however, was challenged from the start by seasonal variability in water flow, and in recent years has been greatly reduced by droughts. Combining hydropower with other alternative energy sources, though, may offer a solution. Solar and wind plants can produce enormous amounts of electricity, but one serious downside is that the energy they produce is not available when there is little sun or wind. While conventional batteries can help with this issue, storing such tremendous volumes of electricity has long been a challenge. A recently proposed system for Hoover Dam could provide an answer, though. The plan suggests building a new pumping station that would be powered by both wind and solar. It would push water from the river back up to Hoover Dam, refilling the lake behind it. The water could be released anytime to power the dam's generators in order to reliably meet demand for electricity. Kelly Sanders, an engineering professor at the University of Southern California, is enthusiastic about the storage plan, saying, "We by the p replace fo solat als are st ons to the What is 1 Inst inves 2 WE dams 3 A neg sys 1 en

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