解
sin(θ)−0.2cos(θ)=9.87.51
解
θ=2.48873…+2πn,θ=1.04764…+2πn
+1
度
θ=142.59422…∘+360∘n,θ=60.02563…∘+360∘n解答ステップ
sin(θ)−0.2cos(θ)=9.87.51
両辺に0.2cos(θ)を足すsin(θ)=0.76632…+0.2cos(θ)
両辺を2乗するsin2(θ)=(0.76632…+0.2cos(θ))2
両辺から(0.76632…+0.2cos(θ))2を引くsin2(θ)−0.58725…−0.30653…cos(θ)−0.04cos2(θ)=0
三角関数の公式を使用して書き換える
−0.58725…+sin2(θ)−0.04cos2(θ)−0.30653…cos(θ)
ピタゴラスの公式を使用する: cos2(x)+sin2(x)=1sin2(x)=1−cos2(x)=−0.58725…+1−cos2(θ)−0.04cos2(θ)−0.30653…cos(θ)
簡素化 −0.58725…+1−cos2(θ)−0.04cos2(θ)−0.30653…cos(θ):−1.04cos2(θ)−0.30653…cos(θ)+0.41274…
−0.58725…+1−cos2(θ)−0.04cos2(θ)−0.30653…cos(θ)
類似した元を足す:−cos2(θ)−0.04cos2(θ)=−1.04cos2(θ)=−0.58725…+1−1.04cos2(θ)−0.30653…cos(θ)
数を足す/引く:−0.58725…+1=0.41274…=−1.04cos2(θ)−0.30653…cos(θ)+0.41274…
=−1.04cos2(θ)−0.30653…cos(θ)+0.41274…
0.41274…−0.30653…cos(θ)−1.04cos2(θ)=0
置換で解く
0.41274…−0.30653…cos(θ)−1.04cos2(θ)=0
仮定:cos(θ)=u0.41274…−0.30653…u−1.04u2=0
0.41274…−0.30653…u−1.04u2=0:u=−2.080.30653…+1.81097…,u=2.081.81097…−0.30653…
0.41274…−0.30653…u−1.04u2=0
標準的な形式で書く ax2+bx+c=0−1.04u2−0.30653…u+0.41274…=0
解くとthe二次式
−1.04u2−0.30653…u+0.41274…=0
二次Equationの公式:
次の場合: a=−1.04,b=−0.30653…,c=0.41274…u1,2=2(−1.04)−(−0.30653…)±(−0.30653…)2−4(−1.04)⋅0.41274…
u1,2=2(−1.04)−(−0.30653…)±(−0.30653…)2−4(−1.04)⋅0.41274…
(−0.30653…)2−4(−1.04)⋅0.41274…=1.81097…
(−0.30653…)2−4(−1.04)⋅0.41274…
規則を適用 −(−a)=a=(−0.30653…)2+4⋅1.04⋅0.41274…
指数の規則を適用する: n が偶数であれば (−a)n=an(−0.30653…)2=0.30653…2=0.30653…2+4⋅0.41274…⋅1.04
数を乗じる:4⋅1.04⋅0.41274…=1.71701…=0.30653…2+1.71701…
0.30653…2=0.09396…=0.09396…+1.71701…
数を足す:0.09396…+1.71701…=1.81097…=1.81097…
u1,2=2(−1.04)−(−0.30653…)±1.81097…
解を分離するu1=2(−1.04)−(−0.30653…)+1.81097…,u2=2(−1.04)−(−0.30653…)−1.81097…
u=2(−1.04)−(−0.30653…)+1.81097…:−2.080.30653…+1.81097…
2(−1.04)−(−0.30653…)+1.81097…
括弧を削除する: (−a)=−a,−(−a)=a=−2⋅1.040.30653…+1.81097…
数を乗じる:2⋅1.04=2.08=−2.080.30653…+1.81097…
分数の規則を適用する: −ba=−ba=−2.080.30653…+1.81097…
u=2(−1.04)−(−0.30653…)−1.81097…:2.081.81097…−0.30653…
2(−1.04)−(−0.30653…)−1.81097…
括弧を削除する: (−a)=−a,−(−a)=a=−2⋅1.040.30653…−1.81097…
数を乗じる:2⋅1.04=2.08=−2.080.30653…−1.81097…
分数の規則を適用する: −b−a=ba0.30653…−1.81097…=−(1.81097…−0.30653…)=2.081.81097…−0.30653…
二次equationの解:u=−2.080.30653…+1.81097…,u=2.081.81097…−0.30653…
代用を戻す u=cos(θ)cos(θ)=−2.080.30653…+1.81097…,cos(θ)=2.081.81097…−0.30653…
cos(θ)=−2.080.30653…+1.81097…,cos(θ)=2.081.81097…−0.30653…
cos(θ)=−2.080.30653…+1.81097…:θ=arccos(−2.080.30653…+1.81097…)+2πn,θ=−arccos(−2.080.30653…+1.81097…)+2πn
cos(θ)=−2.080.30653…+1.81097…
三角関数の逆数プロパティを適用する
cos(θ)=−2.080.30653…+1.81097…
以下の一般解 cos(θ)=−2.080.30653…+1.81097…cos(x)=−a⇒x=arccos(−a)+2πn,x=−arccos(−a)+2πnθ=arccos(−2.080.30653…+1.81097…)+2πn,θ=−arccos(−2.080.30653…+1.81097…)+2πn
θ=arccos(−2.080.30653…+1.81097…)+2πn,θ=−arccos(−2.080.30653…+1.81097…)+2πn
cos(θ)=2.081.81097…−0.30653…:θ=arccos(2.081.81097…−0.30653…)+2πn,θ=2π−arccos(2.081.81097…−0.30653…)+2πn
cos(θ)=2.081.81097…−0.30653…
三角関数の逆数プロパティを適用する
cos(θ)=2.081.81097…−0.30653…
以下の一般解 cos(θ)=2.081.81097…−0.30653…cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnθ=arccos(2.081.81097…−0.30653…)+2πn,θ=2π−arccos(2.081.81097…−0.30653…)+2πn
θ=arccos(2.081.81097…−0.30653…)+2πn,θ=2π−arccos(2.081.81097…−0.30653…)+2πn
すべての解を組み合わせるθ=arccos(−2.080.30653…+1.81097…)+2πn,θ=−arccos(−2.080.30653…+1.81097…)+2πn,θ=arccos(2.081.81097…−0.30653…)+2πn,θ=2π−arccos(2.081.81097…−0.30653…)+2πn
元のequationに当てはめて解を検算する
sin(θ)−0.2cos(θ)=9.87.51 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(−2.080.30653…+1.81097…)+2πn:真
arccos(−2.080.30653…+1.81097…)+2πn
挿入 n=1arccos(−2.080.30653…+1.81097…)+2π1
sin(θ)−0.2cos(θ)=9.87.51の挿入向けθ=arccos(−2.080.30653…+1.81097…)+2π1sin(arccos(−2.080.30653…+1.81097…)+2π1)−0.2cos(arccos(−2.080.30653…+1.81097…)+2π1)=9.87.51
改良0.76632…=0.76632…
⇒真
解答を確認する −arccos(−2.080.30653…+1.81097…)+2πn:偽
−arccos(−2.080.30653…+1.81097…)+2πn
挿入 n=1−arccos(−2.080.30653…+1.81097…)+2π1
sin(θ)−0.2cos(θ)=9.87.51の挿入向けθ=−arccos(−2.080.30653…+1.81097…)+2π1sin(−arccos(−2.080.30653…+1.81097…)+2π1)−0.2cos(−arccos(−2.080.30653…+1.81097…)+2π1)=9.87.51
改良−0.44858…=0.76632…
⇒偽
解答を確認する arccos(2.081.81097…−0.30653…)+2πn:真
arccos(2.081.81097…−0.30653…)+2πn
挿入 n=1arccos(2.081.81097…−0.30653…)+2π1
sin(θ)−0.2cos(θ)=9.87.51の挿入向けθ=arccos(2.081.81097…−0.30653…)+2π1sin(arccos(2.081.81097…−0.30653…)+2π1)−0.2cos(arccos(2.081.81097…−0.30653…)+2π1)=9.87.51
改良0.76632…=0.76632…
⇒真
解答を確認する 2π−arccos(2.081.81097…−0.30653…)+2πn:偽
2π−arccos(2.081.81097…−0.30653…)+2πn
挿入 n=12π−arccos(2.081.81097…−0.30653…)+2π1
sin(θ)−0.2cos(θ)=9.87.51の挿入向けθ=2π−arccos(2.081.81097…−0.30653…)+2π1sin(2π−arccos(2.081.81097…−0.30653…)+2π1)−0.2cos(2π−arccos(2.081.81097…−0.30653…)+2π1)=9.87.51
改良−0.96617…=0.76632…
⇒偽
θ=arccos(−2.080.30653…+1.81097…)+2πn,θ=arccos(2.081.81097…−0.30653…)+2πn
10進法形式で解を証明するθ=2.48873…+2πn,θ=1.04764…+2πn