解
0.1cos(x)+0.45sin(x)=0.3125
解
x=0.52624…+2πn,x=π−0.96358…+2πn
+1
度
x=30.15154…∘+360∘n,x=124.79083…∘+360∘n解答ステップ
0.1cos(x)+0.45sin(x)=0.3125
両辺から0.45sin(x)を引く0.1cos(x)=0.3125−0.45sin(x)
両辺を2乗する(0.1cos(x))2=(0.3125−0.45sin(x))2
両辺から(0.3125−0.45sin(x))2を引く0.01cos2(x)−0.09765625+0.28125sin(x)−0.2025sin2(x)=0
三角関数の公式を使用して書き換える
−0.09765625+0.01cos2(x)−0.2025sin2(x)+0.28125sin(x)
ピタゴラスの公式を使用する: cos2(x)+sin2(x)=1cos2(x)=1−sin2(x)=−0.09765625+0.01(1−sin2(x))−0.2025sin2(x)+0.28125sin(x)
簡素化 −0.09765625+0.01(1−sin2(x))−0.2025sin2(x)+0.28125sin(x):0.28125sin(x)−0.2125sin2(x)−0.08765625
−0.09765625+0.01(1−sin2(x))−0.2025sin2(x)+0.28125sin(x)
拡張 0.01(1−sin2(x)):0.01−0.01sin2(x)
0.01(1−sin2(x))
分配法則を適用する: a(b−c)=ab−aca=0.01,b=1,c=sin2(x)=0.01⋅1−0.01sin2(x)
=1⋅0.01−0.01sin2(x)
数を乗じる:1⋅0.01=0.01=0.01−0.01sin2(x)
=−0.09765625+0.01−0.01sin2(x)−0.2025sin2(x)+0.28125sin(x)
簡素化 −0.09765625+0.01−0.01sin2(x)−0.2025sin2(x)+0.28125sin(x):0.28125sin(x)−0.2125sin2(x)−0.08765625
−0.09765625+0.01−0.01sin2(x)−0.2025sin2(x)+0.28125sin(x)
類似した元を足す:−0.01sin2(x)−0.2025sin2(x)=−0.2125sin2(x)=−0.09765625+0.01−0.2125sin2(x)+0.28125sin(x)
数を足す/引く:−0.09765625+0.01=−0.08765625=0.28125sin(x)−0.2125sin2(x)−0.08765625
=0.28125sin(x)−0.2125sin2(x)−0.08765625
=0.28125sin(x)−0.2125sin2(x)−0.08765625
−0.08765625−0.2125sin2(x)+0.28125sin(x)=0
置換で解く
−0.08765625−0.2125sin2(x)+0.28125sin(x)=0
仮定:sin(x)=u−0.08765625−0.2125u2+0.28125u=0
−0.08765625−0.2125u2+0.28125u=0:u=0.4250.28125−0.00459375,u=0.4250.28125+0.00459375
−0.08765625−0.2125u2+0.28125u=0
標準的な形式で書く ax2+bx+c=0−0.2125u2+0.28125u−0.08765625=0
解くとthe二次式
−0.2125u2+0.28125u−0.08765625=0
二次Equationの公式:
次の場合: a=−0.2125,b=0.28125,c=−0.08765625u1,2=2(−0.2125)−0.28125±0.281252−4(−0.2125)(−0.08765625)
u1,2=2(−0.2125)−0.28125±0.281252−4(−0.2125)(−0.08765625)
0.281252−4(−0.2125)(−0.08765625)=0.00459375
0.281252−4(−0.2125)(−0.08765625)
規則を適用 −(−a)=a=0.281252−4⋅0.2125⋅0.08765625
数を乗じる:4⋅0.2125⋅0.08765625=0.0745078125=0.281252−0.0745078125
0.281252=0.0791015625=0.0791015625−0.07450…
数を引く:0.0791015625−0.07450…=0.00459375=0.00459375
u1,2=2(−0.2125)−0.28125±0.00459375
解を分離するu1=2(−0.2125)−0.28125+0.00459375,u2=2(−0.2125)−0.28125−0.00459375
u=2(−0.2125)−0.28125+0.00459375:0.4250.28125−0.00459375
2(−0.2125)−0.28125+0.00459375
括弧を削除する: (−a)=−a=−2⋅0.2125−0.28125+0.00459375
数を乗じる:2⋅0.2125=0.425=−0.425−0.28125+0.00459375
分数の規則を適用する: −b−a=ba−0.28125+0.00459375=−(0.28125−0.00459375)=0.4250.28125−0.00459375
u=2(−0.2125)−0.28125−0.00459375:0.4250.28125+0.00459375
2(−0.2125)−0.28125−0.00459375
括弧を削除する: (−a)=−a=−2⋅0.2125−0.28125−0.00459375
数を乗じる:2⋅0.2125=0.425=−0.425−0.28125−0.00459375
分数の規則を適用する: −b−a=ba−0.28125−0.00459375=−(0.28125+0.00459375)=0.4250.28125+0.00459375
二次equationの解:u=0.4250.28125−0.00459375,u=0.4250.28125+0.00459375
代用を戻す u=sin(x)sin(x)=0.4250.28125−0.00459375,sin(x)=0.4250.28125+0.00459375
sin(x)=0.4250.28125−0.00459375,sin(x)=0.4250.28125+0.00459375
sin(x)=0.4250.28125−0.00459375:x=arcsin(0.4250.28125−0.00459375)+2πn,x=π−arcsin(0.4250.28125−0.00459375)+2πn
sin(x)=0.4250.28125−0.00459375
三角関数の逆数プロパティを適用する
sin(x)=0.4250.28125−0.00459375
以下の一般解 sin(x)=0.4250.28125−0.00459375sin(x)=a⇒x=arcsin(a)+2πn,x=π−arcsin(a)+2πnx=arcsin(0.4250.28125−0.00459375)+2πn,x=π−arcsin(0.4250.28125−0.00459375)+2πn
x=arcsin(0.4250.28125−0.00459375)+2πn,x=π−arcsin(0.4250.28125−0.00459375)+2πn
sin(x)=0.4250.28125+0.00459375:x=arcsin(0.4250.28125+0.00459375)+2πn,x=π−arcsin(0.4250.28125+0.00459375)+2πn
sin(x)=0.4250.28125+0.00459375
三角関数の逆数プロパティを適用する
sin(x)=0.4250.28125+0.00459375
以下の一般解 sin(x)=0.4250.28125+0.00459375sin(x)=a⇒x=arcsin(a)+2πn,x=π−arcsin(a)+2πnx=arcsin(0.4250.28125+0.00459375)+2πn,x=π−arcsin(0.4250.28125+0.00459375)+2πn
x=arcsin(0.4250.28125+0.00459375)+2πn,x=π−arcsin(0.4250.28125+0.00459375)+2πn
すべての解を組み合わせるx=arcsin(0.4250.28125−0.00459375)+2πn,x=π−arcsin(0.4250.28125−0.00459375)+2πn,x=arcsin(0.4250.28125+0.00459375)+2πn,x=π−arcsin(0.4250.28125+0.00459375)+2πn
元のequationに当てはめて解を検算する
0.1cos(x)+0.45sin(x)=0.3125 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 arcsin(0.4250.28125−0.00459375)+2πn:真
arcsin(0.4250.28125−0.00459375)+2πn
挿入 n=1arcsin(0.4250.28125−0.00459375)+2π1
0.1cos(x)+0.45sin(x)=0.3125の挿入向けx=arcsin(0.4250.28125−0.00459375)+2π10.1cos(arcsin(0.4250.28125−0.00459375)+2π1)+0.45sin(arcsin(0.4250.28125−0.00459375)+2π1)=0.3125
改良0.3125=0.3125
⇒真
解答を確認する π−arcsin(0.4250.28125−0.00459375)+2πn:偽
π−arcsin(0.4250.28125−0.00459375)+2πn
挿入 n=1π−arcsin(0.4250.28125−0.00459375)+2π1
0.1cos(x)+0.45sin(x)=0.3125の挿入向けx=π−arcsin(0.4250.28125−0.00459375)+2π10.1cos(π−arcsin(0.4250.28125−0.00459375)+2π1)+0.45sin(π−arcsin(0.4250.28125−0.00459375)+2π1)=0.3125
改良0.13956…=0.3125
⇒偽
解答を確認する arcsin(0.4250.28125+0.00459375)+2πn:偽
arcsin(0.4250.28125+0.00459375)+2πn
挿入 n=1arcsin(0.4250.28125+0.00459375)+2π1
0.1cos(x)+0.45sin(x)=0.3125の挿入向けx=arcsin(0.4250.28125+0.00459375)+2π10.1cos(arcsin(0.4250.28125+0.00459375)+2π1)+0.45sin(arcsin(0.4250.28125+0.00459375)+2π1)=0.3125
改良0.42661…=0.3125
⇒偽
解答を確認する π−arcsin(0.4250.28125+0.00459375)+2πn:真
π−arcsin(0.4250.28125+0.00459375)+2πn
挿入 n=1π−arcsin(0.4250.28125+0.00459375)+2π1
0.1cos(x)+0.45sin(x)=0.3125の挿入向けx=π−arcsin(0.4250.28125+0.00459375)+2π10.1cos(π−arcsin(0.4250.28125+0.00459375)+2π1)+0.45sin(π−arcsin(0.4250.28125+0.00459375)+2π1)=0.3125
改良0.3125=0.3125
⇒真
x=arcsin(0.4250.28125−0.00459375)+2πn,x=π−arcsin(0.4250.28125+0.00459375)+2πn
10進法形式で解を証明するx=0.52624…+2πn,x=π−0.96358…+2πn