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数学 高校生

この問題を、自分は次のように考えたのですが、なぜ自分の考えた方ではダメなのでしょうか?

例題 154 三角方程式の解法(和と積の公式利用) ate 254 KOsost のとき,次の方程式を解け。 25 cos 20+cos 30+cos 40=0 2倍角,3倍角の公式を利用し, cos@ の4次方程式にして解くのは計算が大変( 2=30 に着目 して, 第1項と第3項の和を積の形に直すと、第て環、 ■基本 三食 指針 照)。そこで、 20+40 2 (8+A) の共通因数が現れる。 asiné Aaie 三角関数の和やれ rsin ( CHART」 1 2項ずつ組み合わせる 2 共通因数の発見 cos0=x とおくと 別解 cos 40=cos 2·20 本 解答(左辺)= (cos40+cos20)+cos30 T 15 証明 40-20 COS +cos30 - = 2 =2cos'20-1 40+20 =2cos 2 +Aia)3DDai+&n-2(2x°-1}-1 よって,左辺は 2x?-1-3x+4x 日+A+2(2x-1)?-1 =8x*+4x°-6x°-3x =2cos 30cos 0+cos30 (+A)e+(日ate土 =cos 30(2cos0+1) よって,与えられた方程式は cos 30(2cos 0+1)=0 Coa 97 8+A=x(2x+1)(4x°-3) ゆえに,方程式は 1 cos 30=0 またはScos0= 2 S. x(2x+1)(4x-3)=0 +したがって ゆえに 0S0ST から 0S30<3π 200S a00 この範囲で cos 30=0 を解くと 6800-(0 x=0, - 200 すなわち 13 Icos 2? 1 土 2 30=27, 2" A 200g π 3 5 2'2 ( 2~) 0g S A cos 0=0, 土 13 5 ーT 6'2'6 よって 0=- π π 20) 2?」 2 0<0ST の範囲でこれを 0S0ST の範囲で cos0= 解くと 1 を解くと 2 0=x 2 π 3 2 5 6' 2' 3 67 π したがって,求める解は リ= (大研度 2 つ日AA 0=エ 5 6'237, 67 ie +le0 (1) の公

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英語 高校生

教えてください! 訳まで教えていただけると助かります!!

十ロ日 amin 年 月 修飾に関する問題0 日 第2回 9別冊解答p.10~15 ad 1ov md S 選択 完成 問題 空所に入るもっとも適切な語(句)を選びなさい。 Dh 0 00oda enoitesmp 1 bn uog 1 Ihave no friends ( O talking to )in English. 3 to talk 4 to talk to (目白大) の talking with ) first prize in the speech contest. 4 won ロロ 2 Iam proud of my son ( (高知大) 3 to win es O having won ② to have won ロロ 3 Ken's been sitting by the phone all day( 3 waiting ) for her to call. の have waited(大阪経済大) 2waited O wait pi y oggo 10 n 1a ansbu Deol bn blod ロロ 4 X: Why has the meeting been put off? Y: Because the meeting room ( important meeting. Owhich reserved 3 who reserved it ) needs to be used for another, more (大 10 2which has reserved の which we reserved (北海学園大) who ロ口 5 The research that Professor Tanaka is conducting will require ( ) of time, money and energy. Da large amount 3a large extent ovsiltuno bof 08 ) of svari uov oodh To 2a large area 大 のa large number TIAU (東北学院大) 6 The cat was ( ) run over by a car. D almost ② dangerously ③less than O mostly (東北学院大) s Lalding them 7 I've got to pay the money back ( O by ) the end of the month. (2) on 3 over のtill (関西学院大) 8 Jack said he broke the window by accident, but I think he did it ( の intentionally ② rapidly 3 carelessly ④ noisily (中央大) 9( ), my reorganization plan has been going very well. O So far 2 Until then 3 In time の By now (同志社女子大)

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英語 高校生

教えてください! 訳も教えてくれたら嬉しいです!!

oni) 年- 月 修飾に関する問題 ① 日 第2回 9別冊解答 p.10~15 O dW TS s Diovs GoT blbona angitasp bnt uog oo 選択 1 空所に入るもっとも適切な語(句)を選びなさい。 問題 ) in English. 1 I have no friends ( O talking to 3 to talk to talk to (目白大) 2 talking with )first prize in the speech contest. 4) Won ロ 2 I am proud of my son( (高知大) 3 to win es O having won ② to have won oved e ロロ 3 Ken's been sitting by the phone all day ( 2waited ) for her to call. の have waited(大阪経済大) 3 waiting m s bnt の 0 wait obournh 2r (8) Oeol ( ロロ 4 X: Why has the meeting been put off? Y: Because the meeting room ( moo ) needs to be used for another, more important meeting. 0which reserved (大育 大 uo lona )19 ② which has reserved ③ who reserved it のwhich we reserved (北海学園大) who 5 The research that Professor Tanaka is conducting will require ( anouesup ses 19wenoj V o joY 0 ) of time, money and energy. Da large amount ③a large extent ai ob ot veri uoy ( 2a large area (大館) のa large number TAU (東北学院大) ) run over byacar. なざい。 ② dangerously ③less than 6 The cat was ( D almost の mostly (東北学院大) 口24 Toay 7 I've got to pay the money back ( O by days and ho usallyis talking them ) the end of the month. (学大) (関西学院大) (2) on 3 Over の till ロ 8 Jack said he broke the window by accident, but I think he did it ( Ointentionally ② rapidly 3 carelessly の noisily (中央大) 9( ), my reorganization plan has been going very well. D So far 2 Until then 3 In time の By now (同志社女子大)

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