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شائع علم المثلثات >

3sec^2(x)+4cos^2(x)=7

الحلّ

3 sec^{2} (x) + 4 cos^{2} (x) = 7

الحلّ

x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn, x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn, x = 2 πn, x = π + 2 πn

درجات

x = 3 0^{\circ} + 36 0^{\circ} n, x = 33 0^{\circ} + 36 0^{\circ} n, x = 15 0^{\circ} + 36 0^{\circ} n, x = 21 0^{\circ} + 36 0^{\circ} n, x = 0^{\circ} + 36 0^{\circ} n, x = 18 0^{\circ} + 36 0^{\circ} n

خطوات الحلّ

3 sec^{2} (x) + 4 cos^{2} (x) = 7

من الطرفين

7

اطرح

3 sec^{2} (x) + 4 cos^{2} (x) - 7 = 0

Rewrite using trig identities

- 7 + 3 sec^{2} (x) + 4 cos^{2} (x)

cos (x) = \frac{1}{sec ( x )}

:Use the basic trigonometric identity

= - 7 + 3 sec^{2} (x) + 4 (\frac{1}{sec ( x )})^{2}

4 (\frac{1}{sec ( x )})^{2} = \frac{4}{sec ^{2} ( x )}

4 (\frac{1}{sec ( x )})^{2}

(\frac{1}{sec ( x )})^{2} = \frac{1}{sec ^{2} ( x )}

(\frac{1}{sec ( x )})^{2}

(\frac{a}{b})^{c} = \frac{a ^{c}}{b ^{c}}

:فعّل قانون القوى

= \frac{1 ^{2}}{sec ^{2} ( x )}

1^{a} = 1

فعّل القانون

1^{2} = 1

= \frac{1}{sec ^{2} ( x )}

= 4 \cdot \frac{1}{sec ^{2} ( x )}

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

:اضرب كسور

= \frac{1 \cdot 4}{sec ^{2} ( x )}

1 \cdot 4 = 4 :

اضرب الأعداد

= \frac{4}{sec ^{2} ( x )}

= - 7 + 3 sec^{2} (x) + \frac{4}{sec ^{2} ( x )}

- 7 + \frac{4}{sec ^{2} ( x )} + 3 sec^{2} (x) = 0

بالاستعانة بطريقة التعويض

- 7 + \frac{4}{sec ^{2} ( x )} + 3 sec^{2} (x) = 0

sec (x) = u :

على افتراض أنّ

- 7 + \frac{4}{u ^{2}} + 3 u^{2} = 0

- 7 + \frac{4}{u ^{2}} + 3 u^{2} = 0 : u = \frac{2 3}{3}, u = - \frac{2 3}{3}, u = 1, u = - 1

- 7 + \frac{4}{u ^{2}} + 3 u^{2} = 0

u^{2}

اضرب الطرفين بـ

- 7 + \frac{4}{u ^{2}} + 3 u^{2} = 0

u^{2}

اضرب الطرفين بـ

- 7 u^{2} + \frac{4}{u ^{2}} u^{2} + 3 u^{2} u^{2} = 0 \cdot u^{2}

بسّط

- 7 u^{2} + \frac{4}{u ^{2}} u^{2} + 3 u^{2} u^{2} = 0 \cdot u^{2}

\frac{4}{u ^{2}} u^{2}

بسّط:

4

\frac{4}{u ^{2}} u^{2}

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

:اضرب كسور

= \frac{4 u ^{2}}{u ^{2}}

u^{2} :

إلغ العوامل المشتركة

= 4

3 u^{2} u^{2}

بسّط:

3 u^{4}

3 u^{2} u^{2}

a^{b} \cdot a^{c} = a^{b + c}

:فعّل قانون القوى

u^{2} u^{2} = u^{2 + 2}

= 3 u^{2 + 2}

2 + 2 = 4 :

اجمع الأعداد

= 3 u^{4}

0 \cdot u^{2}

بسّط:

0

0 \cdot u^{2}

0 \cdot a = 0

فعّل القانون

= 0

- 7 u^{2} + 4 + 3 u^{4} = 0

- 7 u^{2} + 4 + 3 u^{4} = 0

- 7 u^{2} + 4 + 3 u^{4} = 0

- 7 u^{2} + 4 + 3 u^{4} = 0

حلّ:

u = \frac{2 3}{3}, u = - \frac{2 3}{3}, u = 1, u = - 1

- 7 u^{2} + 4 + 3 u^{4} = 0

a_{n} x^{n} + \dots + a_{1} x + a_{0} = 0

اكتب بالصورة الاعتياديّة

3 u^{4} - 7 u^{2} + 4 = 0

v^{2} = u^{4}

وكذلك

v = u^{2}

اكتب المعادلة مجددًا، بحيث أنّ

3 v^{2} - 7 v + 4 = 0

3 v^{2} - 7 v + 4 = 0

حلّ:

v = \frac{4}{3}, v = 1

3 v^{2} - 7 v + 4 = 0

حلّ بالاستعانة بالصيغة التربيعيّة

3 v^{2} - 7 v + 4 = 0

الصيغة لحلّ المعادلة التربيعيّة

a = 3, b = - 7, c = 4

لـ

v_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 3 \cdot 4}{2 \cdot 3}

v_{1, 2} = \frac{- ( - 7 ) \pm ( - 7 ) ^{2} - 4 \cdot 3 \cdot 4}{2 \cdot 3}

(- 7)^{2} - 4 \cdot 3 \cdot 4 = 1

(- 7)^{2} - 4 \cdot 3 \cdot 4

زوجيّ n

إذا تحقّق أنّ

, (- a)^{n} = a^{n}

:فعّل قانون القوى

(- 7)^{2} = 7^{2}

= 7^{2} - 4 \cdot 3 \cdot 4

4 \cdot 3 \cdot 4 = 48 :

اضرب الأعداد

= 7^{2} - 48

7^{2} = 49

= 49 - 48

49 - 48 = 1 :

اطرح الأعداد

= 1

1 = 1

فعّل القانون

= 1

v_{1, 2} = \frac{- ( - 7 ) \pm 1}{2 \cdot 3}

Separate the solutions

v_{1} = \frac{- ( - 7 ) + 1}{2 \cdot 3}, v_{2} = \frac{- ( - 7 ) - 1}{2 \cdot 3}

v = \frac{- ( - 7 ) + 1}{2 \cdot 3} : \frac{4}{3}

\frac{- ( - 7 ) + 1}{2 \cdot 3}

- (- a) = a

فعّل القانون

= \frac{7 + 1}{2 \cdot 3}

7 + 1 = 8 :

اجمع الأعداد

= \frac{8}{2 \cdot 3}

2 \cdot 3 = 6 :

اضرب الأعداد

= \frac{8}{6}

2 :

إلغ العوامل المشتركة

= \frac{4}{3}

v = \frac{- ( - 7 ) - 1}{2 \cdot 3} : 1

\frac{- ( - 7 ) - 1}{2 \cdot 3}

- (- a) = a

فعّل القانون

= \frac{7 - 1}{2 \cdot 3}

7 - 1 = 6 :

اطرح الأعداد

= \frac{6}{2 \cdot 3}

2 \cdot 3 = 6 :

اضرب الأعداد

= \frac{6}{6}

\frac{a}{a} = 1

فعّل القانون

= 1

حلول المعادلة التربيعيّة هي

v = \frac{4}{3}, v = 1

v = \frac{4}{3}, v = 1

Substitute back

v = u^{2},

solve for

u

u^{2} = \frac{4}{3}

حلّ:

u = \frac{2 3}{3}, u = - \frac{2 3}{3}

u^{2} = \frac{4}{3}

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

الحلول هي

x^{2} = f (a)

لـ

u = \frac{4}{3}, u = - \frac{4}{3}

\frac{4}{3} = \frac{2 3}{3}

\frac{4}{3}

a \geq 0, b \geq 0

بافتراض أنّ

n \frac{a}{b} = \frac{n a}{n b}

:فعّل قانون الجذور

= \frac{4}{3}

4 = 2

4

4 = 2^{2} :

حلّل العدد لعوامله أوّليّة

= 2^{2}

n a^{n} = a

:فعْل قانون الجذور

2^{2} = 2

= 2

= \frac{2}{3}

\frac{2}{3}

حوّل لصيغة عدد كسريّ:

\frac{2 3}{3}

\frac{2}{3}

\frac{3}{3}

اضرب بالمرافق

= \frac{2 3}{3 3}

33 = 3

33

a a = a

:فعْل قانون الجذور

33 = 3

= 3

= \frac{2 3}{3}

= \frac{2 3}{3}

- \frac{4}{3} = - \frac{2 3}{3}

- \frac{4}{3}

\frac{4}{3}

بسّط:

\frac{2}{3}

\frac{4}{3}

a \geq 0, b \geq 0

بافتراض أنّ

n \frac{a}{b} = \frac{n a}{n b}

:فعّل قانون الجذور

= \frac{4}{3}

4 = 2

4

4 = 2^{2} :

حلّل العدد لعوامله أوّليّة

= 2^{2}

n a^{n} = a

:فعْل قانون الجذور

2^{2} = 2

= 2

= \frac{2}{3}

= - \frac{2}{3}

- \frac{2}{3}

حوّل لصيغة عدد كسريّ:

- \frac{2 3}{3}

- \frac{2}{3}

\frac{3}{3}

اضرب بالمرافق

= - \frac{2 3}{3 3}

33 = 3

33

a a = a

:فعْل قانون الجذور

33 = 3

= 3

= - \frac{2 3}{3}

= - \frac{2 3}{3}

u = \frac{2 3}{3}, u = - \frac{2 3}{3}

u^{2} = 1

حلّ:

u = 1, u = - 1

u^{2} = 1

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

الحلول هي

x^{2} = f (a)

لـ

u = 1, u = - 1

1 = 1

1

1 = 1

فعّل القانون

= 1

- 1 = - 1

- 1

1 = 1

فعّل القانون

= - 1

u = 1, u = - 1

The solutions are

u = \frac{2 3}{3}, u = - \frac{2 3}{3}, u = 1, u = - 1

u = \frac{2 3}{3}, u = - \frac{2 3}{3}, u = 1, u = - 1

افحص الإجبات

جد نقاط غير معرّفة:

u = 0

وقم بمساواتها لصفر

- 7 + \frac{4}{u ^{2}} + 3 u^{2}

خذ المقامات في

u^{2} = 0

حلّ:

u = 0

u^{2} = 0

x^{n} = 0 \Rightarrow x = 0

فعّل القانون

u = 0

النقاط التالية غير معرّفة

u = 0

ضمّ النقاط غير المعرّفة مع الحلول

u = \frac{2 3}{3}, u = - \frac{2 3}{3}, u = 1, u = - 1

u = sec (x)

استبدل مجددًا

sec (x) = \frac{2 3}{3}, sec (x) = - \frac{2 3}{3}, sec (x) = 1, sec (x) = - 1

sec (x) = \frac{2 3}{3}, sec (x) = - \frac{2 3}{3}, sec (x) = 1, sec (x) = - 1

sec (x) = \frac{2 3}{3} : x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

sec (x) = \frac{2 3}{3}

sec (x) = \frac{2 3}{3} :

حلول عامّة لـ

sec (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sec (x) 1 \frac{2 3}{3} 22 Undefined - 2 - 2 - \frac{2 3}{3} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sec (x) - 1 - \frac{2 3}{3} - 2 - 2 Undefined 22 \frac{2 3}{3}

x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn

sec (x) = - \frac{2 3}{3} : x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn

sec (x) = - \frac{2 3}{3}

sec (x) = - \frac{2 3}{3} :

حلول عامّة لـ

sec (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sec (x) 1 \frac{2 3}{3} 22 Undefined - 2 - 2 - \frac{2 3}{3} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sec (x) - 1 - \frac{2 3}{3} - 2 - 2 Undefined 22 \frac{2 3}{3}

x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn

x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn

sec (x) = 1 : x = 2 πn

sec (x) = 1

sec (x) = 1 :

حلول عامّة لـ

sec (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sec (x) 1 \frac{2 3}{3} 22 Undefined - 2 - 2 - \frac{2 3}{3} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sec (x) - 1 - \frac{2 3}{3} - 2 - 2 Undefined 22 \frac{2 3}{3}

x = 0 + 2 πn

x = 0 + 2 πn

x = 0 + 2 πn

حلّ:

x = 2 πn

x = 0 + 2 πn

0 + 2 πn = 2 πn

x = 2 πn

x = 2 πn

sec (x) = - 1 : x = π + 2 πn

sec (x) = - 1

sec (x) = - 1 :

حلول عامّة لـ

sec (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sec (x) 1 \frac{2 3}{3} 22 Undefined - 2 - 2 - \frac{2 3}{3} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sec (x) - 1 - \frac{2 3}{3} - 2 - 2 Undefined 22 \frac{2 3}{3}

x = π + 2 πn

x = π + 2 πn

وحّد الحلول

x = \frac{π}{6} + 2 πn, x = \frac{11 π}{6} + 2 πn, x = \frac{5 π}{6} + 2 πn, x = \frac{7 π}{6} + 2 πn, x = 2 πn, x = π + 2 πn

رسم

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