解
0=1.2209⋅cos(x)+0.0422⋅cos(2⋅x)
解
x=1.53630…+2πn,x=2π−1.53630…+2πn
+1
度
x=88.02390…∘+360∘n,x=271.97609…∘+360∘n解答ステップ
0=1.2209cos(x)+0.0422cos(2x)
辺を交換する1.2209cos(x)+0.0422cos(2x)=0
三角関数の公式を使用して書き換える
0.0422cos(2x)+1.2209cos(x)
2倍角の公式を使用: cos(2x)=2cos2(x)−1=0.0422(2cos2(x)−1)+1.2209cos(x)
(−1+2cos2(x))⋅0.0422+1.2209cos(x)=0
置換で解く
(−1+2cos2(x))⋅0.0422+1.2209cos(x)=0
仮定:cos(x)=u(−1+2u2)⋅0.0422+1.2209u=0
(−1+2u2)⋅0.0422+1.2209u=0:u=0.1688−1.2209+1.50484353,u=0.1688−1.2209−1.50484353
(−1+2u2)⋅0.0422+1.2209u=0
拡張 (−1+2u2)⋅0.0422+1.2209u:−0.0422+0.0844u2+1.2209u
(−1+2u2)⋅0.0422+1.2209u
=0.0422(−1+2u2)+1.2209u
拡張 0.0422(−1+2u2):−0.0422+0.0844u2
0.0422(−1+2u2)
分配法則を適用する: a(b+c)=ab+aca=0.0422,b=−1,c=2u2=0.0422(−1)+0.0422⋅2u2
マイナス・プラスの規則を適用する+(−a)=−a=−1⋅0.0422+2⋅0.0422u2
簡素化 −1⋅0.0422+2⋅0.0422u2:−0.0422+0.0844u2
−1⋅0.0422+2⋅0.0422u2
数を乗じる:1⋅0.0422=0.0422=−0.0422+2⋅0.0422u2
数を乗じる:2⋅0.0422=0.0844=−0.0422+0.0844u2
=−0.0422+0.0844u2
=−0.0422+0.0844u2+1.2209u
−0.0422+0.0844u2+1.2209u=0
標準的な形式で書く ax2+bx+c=00.0844u2+1.2209u−0.0422=0
解くとthe二次式
0.0844u2+1.2209u−0.0422=0
二次Equationの公式:
次の場合: a=0.0844,b=1.2209,c=−0.0422u1,2=2⋅0.0844−1.2209±1.22092−4⋅0.0844(−0.0422)
u1,2=2⋅0.0844−1.2209±1.22092−4⋅0.0844(−0.0422)
1.22092−4⋅0.0844(−0.0422)=1.50484353
1.22092−4⋅0.0844(−0.0422)
規則を適用 −(−a)=a=1.22092+4⋅0.0844⋅0.0422
数を乗じる:4⋅0.0844⋅0.0422=0.01424672=1.22092+0.01424672
1.22092=1.49059681=1.49059681+0.01424672
数を足す:1.49059681+0.01424672=1.50484353=1.50484353
u1,2=2⋅0.0844−1.2209±1.50484353
解を分離するu1=2⋅0.0844−1.2209+1.50484353,u2=2⋅0.0844−1.2209−1.50484353
u=2⋅0.0844−1.2209+1.50484353:0.1688−1.2209+1.50484353
2⋅0.0844−1.2209+1.50484353
数を乗じる:2⋅0.0844=0.1688=0.1688−1.2209+1.50484353
u=2⋅0.0844−1.2209−1.50484353:0.1688−1.2209−1.50484353
2⋅0.0844−1.2209−1.50484353
数を乗じる:2⋅0.0844=0.1688=0.1688−1.2209−1.50484353
二次equationの解:u=0.1688−1.2209+1.50484353,u=0.1688−1.2209−1.50484353
代用を戻す u=cos(x)cos(x)=0.1688−1.2209+1.50484353,cos(x)=0.1688−1.2209−1.50484353
cos(x)=0.1688−1.2209+1.50484353,cos(x)=0.1688−1.2209−1.50484353
cos(x)=0.1688−1.2209+1.50484353:x=arccos(0.1688−1.2209+1.50484353)+2πn,x=2π−arccos(0.1688−1.2209+1.50484353)+2πn
cos(x)=0.1688−1.2209+1.50484353
三角関数の逆数プロパティを適用する
cos(x)=0.1688−1.2209+1.50484353
以下の一般解 cos(x)=0.1688−1.2209+1.50484353cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnx=arccos(0.1688−1.2209+1.50484353)+2πn,x=2π−arccos(0.1688−1.2209+1.50484353)+2πn
x=arccos(0.1688−1.2209+1.50484353)+2πn,x=2π−arccos(0.1688−1.2209+1.50484353)+2πn
cos(x)=0.1688−1.2209−1.50484353:解なし
cos(x)=0.1688−1.2209−1.50484353
−1≤cos(x)≤1解なし
すべての解を組み合わせるx=arccos(0.1688−1.2209+1.50484353)+2πn,x=2π−arccos(0.1688−1.2209+1.50484353)+2πn
10進法形式で解を証明するx=1.53630…+2πn,x=2π−1.53630…+2πn