해법
sin2(x)=cos3(x)
해법
x=0.71532…+2πn,x=2π−0.71532…+2πn
+1
도
x=40.98531…∘+360∘n,x=319.01468…∘+360∘n솔루션 단계
sin2(x)=cos3(x)
빼다 cos3(x) 양쪽에서sin2(x)−cos3(x)=0
삼각성을 사용하여 다시 쓰기
−cos3(x)+sin2(x)
피타고라스 정체성 사용: cos2(x)+sin2(x)=1sin2(x)=1−cos2(x)=−cos3(x)+1−cos2(x)
1−cos2(x)−cos3(x)=0
대체로 해결
1−cos2(x)−cos3(x)=0
하게: cos(x)=u1−u2−u3=0
1−u2−u3=0:u≈0.75487…
1−u2−u3=0
표준 양식으로 작성 anxn+…+a1x+a0=0−u3−u2+1=0
다음을 위한 하나의 솔루션 찾기 −u3−u2+1=0 뉴턴-랩슨을 이용하여:u≈0.75487…
−u3−u2+1=0
뉴턴-랩슨 근사 정의
f(u)=−u3−u2+1
f′(u)찾다 :−3u2−2u
dud(−u3−u2+1)
합계/차이 규칙 적용: (f±g)′=f′±g′=−dud(u3)−dud(u2)+dud(1)
dud(u3)=3u2
dud(u3)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=3u3−1
단순화=3u2
dud(u2)=2u
dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=2u2−1
단순화=2u
dud(1)=0
dud(1)
상수의 도함수: dxd(a)=0=0
=−3u2−2u+0
단순화=−3u2−2u
렛 u0=1계산하다 un+1 까지 Δun+1<0.000001
u1=0.8:Δu1=0.2
f(u0)=−13−12+1=−1f′(u0)=−3⋅12−2⋅1=−5u1=0.8
Δu1=∣0.8−1∣=0.2Δu1=0.2
u2=0.75681…:Δu2=0.04318…
f(u1)=−0.83−0.82+1=−0.152f′(u1)=−3⋅0.82−2⋅0.8=−3.52u2=0.75681…
Δu2=∣0.75681…−0.8∣=0.04318…Δu2=0.04318…
u3=0.75488…:Δu3=0.00193…
f(u2)=−0.75681…3−0.75681…2+1=−0.00625…f′(u2)=−3⋅0.75681…2−2⋅0.75681…=−3.23195…u3=0.75488…
Δu3=∣0.75488…−0.75681…∣=0.00193…Δu3=0.00193…
u4=0.75487…:Δu4=3.80818E−6
f(u3)=−0.75488…3−0.75488…2+1=−0.00001…f′(u3)=−3⋅0.75488…2−2⋅0.75488…=−3.21930…u4=0.75487…
Δu4=∣0.75487…−0.75488…∣=3.80818E−6Δu4=3.80818E−6
u5=0.75487…:Δu5=1.47065E−11
f(u4)=−0.75487…3−0.75487…2+1=−4.73444E−11f′(u4)=−3⋅0.75487…2−2⋅0.75487…=−3.21927…u5=0.75487…
Δu5=∣0.75487…−0.75487…∣=1.47065E−11Δu5=1.47065E−11
u≈0.75487…
긴 나눗셈 적용:u−0.75487…−u3−u2+1=−u2−1.75487…u−1.32471…
−u2−1.75487…u−1.32471…≈0
다음을 위한 하나의 솔루션 찾기 −u2−1.75487…u−1.32471…=0 뉴턴-랩슨을 이용하여:솔루션 없음 u∈R
−u2−1.75487…u−1.32471…=0
뉴턴-랩슨 근사 정의
f(u)=−u2−1.75487…u−1.32471…
f′(u)찾다 :−2u−1.75487…
dud(−u2−1.75487…u−1.32471…)
합계/차이 규칙 적용: (f±g)′=f′±g′=−dud(u2)−dud(1.75487…u)−dud(1.32471…)
dud(u2)=2u
dud(u2)
전원 규칙을 적용합니다: dxd(xa)=a⋅xa−1=2u2−1
단순화=2u
dud(1.75487…u)=1.75487…
dud(1.75487…u)
정수를 빼라: (a⋅f)′=a⋅f′=1.75487…dudu
공통 도함수 적용: dudu=1=1.75487…⋅1
단순화=1.75487…
dud(1.32471…)=0
dud(1.32471…)
상수의 도함수: dxd(a)=0=0
=−2u−1.75487…−0
단순화=−2u−1.75487…
렛 u0=−1계산하다 un+1 까지 Δun+1<0.000001
u1=1.32471…:Δu1=2.32471…
f(u0)=−(−1)2−1.75487…(−1)−1.32471…=−0.56984…f′(u0)=−2(−1)−1.75487…=0.24512…u1=1.32471…
Δu1=∣1.32471…−(−1)∣=2.32471…Δu1=2.32471…
u2=0.09766…:Δu2=1.22705…
f(u1)=−1.32471…2−1.75487…⋅1.32471…−1.32471…=−5.40431…f′(u1)=−2⋅1.32471…−1.75487…=−4.40431…u2=0.09766…
Δu2=∣0.09766…−1.32471…∣=1.22705…Δu2=1.22705…
u3=−0.67437…:Δu3=0.77204…
f(u2)=−0.09766…2−1.75487…⋅0.09766…−1.32471…=−1.50565…f′(u2)=−2⋅0.09766…−1.75487…=−1.95021…u3=−0.67437…
Δu3=∣−0.67437…−0.09766…∣=0.77204…Δu3=0.77204…
u4=−2.14204…:Δu4=1.46766…
f(u3)=−(−0.67437…)2−1.75487…(−0.67437…)−1.32471…=−0.59605…f′(u3)=−2(−0.67437…)−1.75487…=−0.40612…u4=−2.14204…
Δu4=∣−2.14204…−(−0.67437…)∣=1.46766…Δu4=1.46766…
u5=−1.29037…:Δu5=0.85166…
f(u4)=−(−2.14204…)2−1.75487…(−2.14204…)−1.32471…=−2.15403…f′(u4)=−2(−2.14204…)−1.75487…=2.52920…u5=−1.29037…
Δu5=∣−1.29037…−(−2.14204…)∣=0.85166…Δu5=0.85166…
u6=−0.41210…:Δu6=0.87826…
f(u5)=−(−1.29037…)2−1.75487…(−1.29037…)−1.32471…=−0.72533…f′(u5)=−2(−1.29037…)−1.75487…=0.82587…u6=−0.41210…
Δu6=∣−0.41210…−(−1.29037…)∣=0.87826…Δu6=0.87826…
u7=−1.24093…:Δu7=0.82882…
f(u6)=−(−0.41210…)2−1.75487…(−0.41210…)−1.32471…=−0.77135…f′(u6)=−2(−0.41210…)−1.75487…=−0.93065…u7=−1.24093…
Δu7=∣−1.24093…−(−0.41210…)∣=0.82882…Δu7=0.82882…
u8=−0.29600…:Δu8=0.94492…
f(u7)=−(−1.24093…)2−1.75487…(−1.24093…)−1.32471…=−0.68694…f′(u7)=−2(−1.24093…)−1.75487…=0.72698…u8=−0.29600…
Δu8=∣−0.29600…−(−1.24093…)∣=0.94492…Δu8=0.94492…
u9=−1.06383…:Δu9=0.76782…
f(u8)=−(−0.29600…)2−1.75487…(−0.29600…)−1.32471…=−0.89288…f′(u8)=−2(−0.29600…)−1.75487…=−1.16286…u9=−1.06383…
Δu9=∣−1.06383…−(−0.29600…)∣=0.76782…Δu9=0.76782…
u10=0.51763…:Δu10=1.58147…
f(u9)=−(−1.06383…)2−1.75487…(−1.06383…)−1.32471…=−0.58956…f′(u9)=−2(−1.06383…)−1.75487…=0.37279…u10=0.51763…
Δu10=∣0.51763…−(−1.06383…)∣=1.58147…Δu10=1.58147…
해결 방법을 찾을 수 없습니다
해결책은u≈0.75487…
뒤로 대체 u=cos(x)cos(x)≈0.75487…
cos(x)≈0.75487…
cos(x)=0.75487…:x=arccos(0.75487…)+2πn,x=2π−arccos(0.75487…)+2πn
cos(x)=0.75487…
트리거 역속성 적용
cos(x)=0.75487…
일반 솔루션 cos(x)=0.75487…cos(x)=a⇒x=arccos(a)+2πn,x=2π−arccos(a)+2πnx=arccos(0.75487…)+2πn,x=2π−arccos(0.75487…)+2πn
x=arccos(0.75487…)+2πn,x=2π−arccos(0.75487…)+2πn
모든 솔루션 결합x=arccos(0.75487…)+2πn,x=2π−arccos(0.75487…)+2πn
해를 10진수 형식으로 표시x=0.71532…+2πn,x=2π−0.71532…+2πn