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شائع علم المثلثات >

cos^4(a)+cos^2(a)=1

الحلّ

cos^{4} (a) + cos^{2} (a) = 1

الحلّ

a = 0.66623 \dots + 2 πn, a = 2 π - 0.66623 \dots + 2 πn, a = 2.47535 \dots + 2 πn, a = - 2.47535 \dots + 2 πn

درجات

a = 38.17270 \dots^{\circ} + 36 0^{\circ} n, a = 321.82729 \dots^{\circ} + 36 0^{\circ} n, a = 141.82729 \dots^{\circ} + 36 0^{\circ} n, a = - 141.82729 \dots^{\circ} + 36 0^{\circ} n

خطوات الحلّ

cos^{4} (a) + cos^{2} (a) = 1

بالاستعانة بطريقة التعويض

cos^{4} (a) + cos^{2} (a) = 1

cos (a) = u :

على افتراض أنّ

u^{4} + u^{2} = 1

u^{4} + u^{2} = 1 : u = \frac{- 1 + 5}{2}, u = - \frac{- 1 + 5}{2}, u = \frac{- 1 - 5}{2}, u = - \frac{- 1 - 5}{2}

u^{4} + u^{2} = 1

انقل

1

إلى الجانب الأيسر

u^{4} + u^{2} = 1

من الطرفين

1

اطرح

u^{4} + u^{2} - 1 = 1 - 1

بسّط

u^{4} + u^{2} - 1 = 0

u^{4} + u^{2} - 1 = 0

v^{2} = u^{4}

وكذلك

v = u^{2}

اكتب المعادلة مجددًا، بحيث أنّ

v^{2} + v - 1 = 0

v^{2} + v - 1 = 0

حلّ:

v = \frac{- 1 + 5}{2}, v = \frac{- 1 - 5}{2}

v^{2} + v - 1 = 0

حلّ بالاستعانة بالصيغة التربيعيّة

v^{2} + v - 1 = 0

الصيغة لحلّ المعادلة التربيعيّة

a = 1, b = 1, c = - 1

لـ

v_{1, 2} = \frac{- 1 \pm 1 ^{2} - 4 \cdot 1 \cdot ( - 1 )}{2 \cdot 1}

v_{1, 2} = \frac{- 1 \pm 1 ^{2} - 4 \cdot 1 \cdot ( - 1 )}{2 \cdot 1}

1^{2} - 4 \cdot 1 \cdot (- 1) = 5

1^{2} - 4 \cdot 1 \cdot (- 1)

1^{a} = 1

فعّل القانون

1^{2} = 1

= 1 - 4 \cdot 1 \cdot (- 1)

- (- a) = a

فعّل القانون

= 1 + 4 \cdot 1 \cdot 1

4 \cdot 1 \cdot 1 = 4 :

اضرب الأعداد

= 1 + 4

1 + 4 = 5 :

اجمع الأعداد

= 5

v_{1, 2} = \frac{- 1 \pm 5}{2 \cdot 1}

Separate the solutions

v_{1} = \frac{- 1 + 5}{2 \cdot 1}, v_{2} = \frac{- 1 - 5}{2 \cdot 1}

v = \frac{- 1 + 5}{2 \cdot 1} : \frac{- 1 + 5}{2}

\frac{- 1 + 5}{2 \cdot 1}

2 \cdot 1 = 2 :

اضرب الأعداد

= \frac{- 1 + 5}{2}

v = \frac{- 1 - 5}{2 \cdot 1} : \frac{- 1 - 5}{2}

\frac{- 1 - 5}{2 \cdot 1}

2 \cdot 1 = 2 :

اضرب الأعداد

= \frac{- 1 - 5}{2}

حلول المعادلة التربيعيّة هي

v = \frac{- 1 + 5}{2}, v = \frac{- 1 - 5}{2}

v = \frac{- 1 + 5}{2}, v = \frac{- 1 - 5}{2}

Substitute back

v = u^{2},

solve for

u

u^{2} = \frac{- 1 + 5}{2}

حلّ:

u = \frac{- 1 + 5}{2}, u = - \frac{- 1 + 5}{2}

u^{2} = \frac{- 1 + 5}{2}

x = f (a), - f (a)

الحلول هي

x^{2} = f (a)

لـ

u = \frac{- 1 + 5}{2}, u = - \frac{- 1 + 5}{2}

u^{2} = \frac{- 1 - 5}{2}

حلّ:

u = \frac{- 1 - 5}{2}, u = - \frac{- 1 - 5}{2}

u^{2} = \frac{- 1 - 5}{2}

x = f (a), - f (a)

الحلول هي

x^{2} = f (a)

لـ

u = \frac{- 1 - 5}{2}, u = - \frac{- 1 - 5}{2}

The solutions are

u = \frac{- 1 + 5}{2}, u = - \frac{- 1 + 5}{2}, u = \frac{- 1 - 5}{2}, u = - \frac{- 1 - 5}{2}

u = cos (a)

استبدل مجددًا

cos (a) = \frac{- 1 + 5}{2}, cos (a) = - \frac{- 1 + 5}{2}, cos (a) = \frac{- 1 - 5}{2}, cos (a) = - \frac{- 1 - 5}{2}

cos (a) = \frac{- 1 + 5}{2}, cos (a) = - \frac{- 1 + 5}{2}, cos (a) = \frac{- 1 - 5}{2}, cos (a) = - \frac{- 1 - 5}{2}

cos (a) = \frac{- 1 + 5}{2} : a = arccos \frac{- 1 + 5}{2} + 2 πn, a = 2 π - arccos \frac{- 1 + 5}{2} + 2 πn

cos (a) = \frac{- 1 + 5}{2}

Apply trig inverse properties

cos (a) = \frac{- 1 + 5}{2}

cos (a) = \frac{- 1 + 5}{2} :

حلول عامّة لـ

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = 2 π - arccos (a) + 2 πn

a = arccos \frac{- 1 + 5}{2} + 2 πn, a = 2 π - arccos \frac{- 1 + 5}{2} + 2 πn

a = arccos \frac{- 1 + 5}{2} + 2 πn, a = 2 π - arccos \frac{- 1 + 5}{2} + 2 πn

cos (a) = - \frac{- 1 + 5}{2} : a = arccos - \frac{- 1 + 5}{2} + 2 πn, a = - arccos - \frac{- 1 + 5}{2} + 2 πn

cos (a) = - \frac{- 1 + 5}{2}

Apply trig inverse properties

cos (a) = - \frac{- 1 + 5}{2}

cos (a) = - \frac{- 1 + 5}{2} :

حلول عامّة لـ

cos (x) = - a \Rightarrow x = arccos (- a) + 2 πn, x = - arccos (- a) + 2 πn

a = arccos - \frac{- 1 + 5}{2} + 2 πn, a = - arccos - \frac{- 1 + 5}{2} + 2 πn

a = arccos - \frac{- 1 + 5}{2} + 2 πn, a = - arccos - \frac{- 1 + 5}{2} + 2 πn

cos (a) = \frac{- 1 - 5}{2} : a = arccos \frac{- 1 - 5}{2} + 2 πn, a = - arccos \frac{- 1 - 5}{2} + 2 πn

cos (a) = \frac{- 1 - 5}{2}

Apply trig inverse properties

cos (a) = \frac{- 1 - 5}{2}

cos (a) = \frac{- 1 - 5}{2} :

حلول عامّة لـ

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = - arccos (a) + 2 πn

a = arccos \frac{- 1 - 5}{2} + 2 πn, a = - arccos \frac{- 1 - 5}{2} + 2 πn

a = arccos \frac{- 1 - 5}{2} + 2 πn, a = - arccos \frac{- 1 - 5}{2} + 2 πn

cos (a) = - \frac{- 1 - 5}{2} : a = arccos - \frac{- 1 - 5}{2} + 2 πn, a = - arccos - \frac{- 1 - 5}{2} + 2 πn

cos (a) = - \frac{- 1 - 5}{2}

Apply trig inverse properties

cos (a) = - \frac{- 1 - 5}{2}

cos (a) = - \frac{- 1 - 5}{2} :

حلول عامّة لـ

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = - arccos (a) + 2 πn

a = arccos - \frac{- 1 - 5}{2} + 2 πn, a = - arccos - \frac{- 1 - 5}{2} + 2 πn

a = arccos - \frac{- 1 - 5}{2} + 2 πn, a = - arccos - \frac{- 1 - 5}{2} + 2 πn

وحّد الحلول

a = arccos \frac{- 1 + 5}{2} + 2 πn, a = 2 π - arccos \frac{- 1 + 5}{2} + 2 πn, a = arccos - \frac{- 1 + 5}{2} + 2 πn, a = - arccos - \frac{- 1 + 5}{2} + 2 πn, a = arccos \frac{- 1 - 5}{2} + 2 πn, a = - arccos \frac{- 1 - 5}{2} + 2 πn, a = arccos - \frac{- 1 - 5}{2} + 2 πn, a = - arccos - \frac{- 1 - 5}{2} + 2 πn

arccos \frac{- 1 - 5}{2} + 2 πn, - arccos \frac{- 1 - 5}{2} + 2 πn, arccos - \frac{- 1 - 5}{2} + 2 πn, - arccos - \frac{- 1 - 5}{2} + 2 πn :

بما أنّ المعادلة غير معرّفة لـ

a = arccos \frac{- 1 + 5}{2} + 2 πn, a = 2 π - arccos \frac{- 1 + 5}{2} + 2 πn, a = arccos - \frac{- 1 + 5}{2} + 2 πn, a = - arccos - \frac{- 1 + 5}{2} + 2 πn

أظهر الحلّ بالتمثيل العشريّ

a = 0.66623 \dots + 2 πn, a = 2 π - 0.66623 \dots + 2 πn, a = 2.47535 \dots + 2 πn, a = - 2.47535 \dots + 2 πn

رسم

أمثلة شائعة

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