解
sin(θ)−5cos(θ)=0.6377
解
θ=2.66345…+2πn,θ=0.87293…+2πn
+1
度
θ=152.60452…∘+360∘n,θ=50.01533…∘+360∘n解答ステップ
sin(θ)−5cos(θ)=0.6377
両辺に5cos(θ)を足すsin(θ)=0.6377+0.2cos(θ)
両辺を2乗するsin2(θ)=(0.6377+0.2cos(θ))2
両辺から(0.6377+0.2cos(θ))2を引くsin2(θ)−0.40666129−0.25508cos(θ)−0.04cos2(θ)=0
三角関数の公式を使用して書き換える
−0.40666129+sin2(θ)−0.04cos2(θ)−0.25508cos(θ)
ピタゴラスの公式を使用する: cos2(x)+sin2(x)=1sin2(x)=1−cos2(x)=−0.40666129+1−cos2(θ)−0.04cos2(θ)−0.25508cos(θ)
簡素化 −0.40666129+1−cos2(θ)−0.04cos2(θ)−0.25508cos(θ):−1.04cos2(θ)−0.25508cos(θ)+0.59333871
−0.40666129+1−cos2(θ)−0.04cos2(θ)−0.25508cos(θ)
類似した元を足す:−cos2(θ)−0.04cos2(θ)=−1.04cos2(θ)=−0.40666129+1−1.04cos2(θ)−0.25508cos(θ)
数を足す/引く:−0.40666129+1=0.59333871=−1.04cos2(θ)−0.25508cos(θ)+0.59333871
=−1.04cos2(θ)−0.25508cos(θ)+0.59333871
0.59333871−0.25508cos(θ)−1.04cos2(θ)=0
置換で解く
0.59333871−0.25508cos(θ)−1.04cos2(θ)=0
仮定:cos(θ)=u0.59333871−0.25508u−1.04u2=0
0.59333871−0.25508u−1.04u2=0:u=−2.080.25508+2.53335484,u=2.082.53335484−0.25508
0.59333871−0.25508u−1.04u2=0
標準的な形式で書く ax2+bx+c=0−1.04u2−0.25508u+0.59333871=0
解くとthe二次式
−1.04u2−0.25508u+0.59333871=0
二次Equationの公式:
次の場合: a=−1.04,b=−0.25508,c=0.59333871u1,2=2(−1.04)−(−0.25508)±(−0.25508)2−4(−1.04)⋅0.59333871
u1,2=2(−1.04)−(−0.25508)±(−0.25508)2−4(−1.04)⋅0.59333871
(−0.25508)2−4(−1.04)⋅0.59333871=2.53335484
(−0.25508)2−4(−1.04)⋅0.59333871
規則を適用 −(−a)=a=(−0.25508)2+4⋅1.04⋅0.59333871
指数の規則を適用する: n が偶数であれば (−a)n=an(−0.25508)2=0.255082=0.255082+4⋅0.59333871⋅1.04
数を乗じる:4⋅1.04⋅0.59333871=2.46828…=0.255082+2.46828…
0.255082=0.0650658064=0.0650658064+2.46828…
数を足す:0.0650658064+2.46828…=2.53335484=2.53335484
u1,2=2(−1.04)−(−0.25508)±2.53335484
解を分離するu1=2(−1.04)−(−0.25508)+2.53335484,u2=2(−1.04)−(−0.25508)−2.53335484
u=2(−1.04)−(−0.25508)+2.53335484:−2.080.25508+2.53335484
2(−1.04)−(−0.25508)+2.53335484
括弧を削除する: (−a)=−a,−(−a)=a=−2⋅1.040.25508+2.53335484
数を乗じる:2⋅1.04=2.08=−2.080.25508+2.53335484
分数の規則を適用する: −ba=−ba=−2.080.25508+2.53335484
u=2(−1.04)−(−0.25508)−2.53335484:2.082.53335484−0.25508
2(−1.04)−(−0.25508)−2.53335484
括弧を削除する: (−a)=−a,−(−a)=a=−2⋅1.040.25508−2.53335484
数を乗じる:2⋅1.04=2.08=−2.080.25508−2.53335484
分数の規則を適用する: −b−a=ba0.25508−2.53335484=−(2.53335484−0.25508)=2.082.53335484−0.25508
二次equationの解:u=−2.080.25508+2.53335484,u=2.082.53335484−0.25508
代用を戻す u=cos(θ)cos(θ)=−2.080.25508+2.53335484,cos(θ)=2.082.53335484−0.25508
cos(θ)=−2.080.25508+2.53335484,cos(θ)=2.082.53335484−0.25508
cos(θ)=−2.080.25508+2.53335484:θ=arccos(−2.080.25508+2.53335484)+2πn,θ=−arccos(−2.080.25508+2.53335484)+2πn
cos(θ)=−2.080.25508+2.53335484
三角関数の逆数プロパティを適用する
cos(θ)=−2.080.25508+2.53335484
以下の一般解 cos(θ)=−2.080.25508+2.53335484cos(x)=−a⇒x=arccos(−a)+2πn,x=−arccos(−a)+2πnθ=arccos(−2.080.25508+2.53335484)+2πn,θ=−arccos(−2.080.25508+2.53335484)+2πn
θ=arccos(−2.080.25508+2.53335484)+2πn,θ=−arccos(−2.080.25508+2.53335484)+2πn
cos(θ)=2.082.53335484−0.25508:θ=arccos(2.082.53335484−0.25508)+2πn,θ=2π−arccos(2.082.53335484−0.25508)+2πn
cos(θ)=2.082.53335484−0.25508
三角関数の逆数プロパティを適用する
cos(θ)=2.082.53335484−0.25508
以下の一般解 cos(θ)=2.082.53335484−0.25508cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnθ=arccos(2.082.53335484−0.25508)+2πn,θ=2π−arccos(2.082.53335484−0.25508)+2πn
θ=arccos(2.082.53335484−0.25508)+2πn,θ=2π−arccos(2.082.53335484−0.25508)+2πn
すべての解を組み合わせるθ=arccos(−2.080.25508+2.53335484)+2πn,θ=−arccos(−2.080.25508+2.53335484)+2πn,θ=arccos(2.082.53335484−0.25508)+2πn,θ=2π−arccos(2.082.53335484−0.25508)+2πn
元のequationに当てはめて解を検算する
sin(θ)−5cos(θ)=0.6377 に当てはめて解を確認する
equationに一致しないものを削除する。
解答を確認する arccos(−2.080.25508+2.53335484)+2πn:真
arccos(−2.080.25508+2.53335484)+2πn
挿入 n=1arccos(−2.080.25508+2.53335484)+2π1
sin(θ)−5cos(θ)=0.6377の挿入向けθ=arccos(−2.080.25508+2.53335484)+2π1sin(arccos(−2.080.25508+2.53335484)+2π1)−5cos(arccos(−2.080.25508+2.53335484)+2π1)=0.6377
改良0.6377=0.6377
⇒真
解答を確認する −arccos(−2.080.25508+2.53335484)+2πn:偽
−arccos(−2.080.25508+2.53335484)+2πn
挿入 n=1−arccos(−2.080.25508+2.53335484)+2π1
sin(θ)−5cos(θ)=0.6377の挿入向けθ=−arccos(−2.080.25508+2.53335484)+2π1sin(−arccos(−2.080.25508+2.53335484)+2π1)−5cos(−arccos(−2.080.25508+2.53335484)+2π1)=0.6377
改良−0.28255…=0.6377
⇒偽
解答を確認する arccos(2.082.53335484−0.25508)+2πn:真
arccos(2.082.53335484−0.25508)+2πn
挿入 n=1arccos(2.082.53335484−0.25508)+2π1
sin(θ)−5cos(θ)=0.6377の挿入向けθ=arccos(2.082.53335484−0.25508)+2π1sin(arccos(2.082.53335484−0.25508)+2π1)−5cos(arccos(2.082.53335484−0.25508)+2π1)=0.6377
改良0.6377=0.6377
⇒真
解答を確認する 2π−arccos(2.082.53335484−0.25508)+2πn:偽
2π−arccos(2.082.53335484−0.25508)+2πn
挿入 n=12π−arccos(2.082.53335484−0.25508)+2π1
sin(θ)−5cos(θ)=0.6377の挿入向けθ=2π−arccos(2.082.53335484−0.25508)+2π1sin(2π−arccos(2.082.53335484−0.25508)+2π1)−5cos(2π−arccos(2.082.53335484−0.25508)+2π1)=0.6377
改良−0.89473…=0.6377
⇒偽
θ=arccos(−2.080.25508+2.53335484)+2πn,θ=arccos(2.082.53335484−0.25508)+2πn
10進法形式で解を証明するθ=2.66345…+2πn,θ=0.87293…+2πn