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شائع علم المثلثات >

3-2cos^2(x)=4sin^2(x)

الحلّ

3 - 2 cos^{2} (x) = 4 sin^{2} (x)

الحلّ

x = \frac{π}{4} + 2 πn, x = \frac{3 π}{4} + 2 πn, x = \frac{5 π}{4} + 2 πn, x = \frac{7 π}{4} + 2 πn

درجات

x = 4 5^{\circ} + 36 0^{\circ} n, x = 13 5^{\circ} + 36 0^{\circ} n, x = 22 5^{\circ} + 36 0^{\circ} n, x = 31 5^{\circ} + 36 0^{\circ} n

خطوات الحلّ

3 - 2 cos^{2} (x) = 4 sin^{2} (x)

من الطرفين

4 sin^{2} (x)

اطرح

3 - 2 cos^{2} (x) - 4 sin^{2} (x) = 0

Rewrite using trig identities

3 - 2 cos^{2} (x) - 4 sin^{2} (x)

cos^{2} (x) + sin^{2} (x) = 1

:فعّل نطريّة فيتاغوروس

cos^{2} (x) = 1 - sin^{2} (x)

= 3 - 2 (1 - sin^{2} (x)) - 4 sin^{2} (x)

3 - 2 (1 - sin^{2} (x)) - 4 sin^{2} (x)

بسّط:

- 2 sin^{2} (x) + 1

3 - 2 (1 - sin^{2} (x)) - 4 sin^{2} (x)

- 2 (1 - sin^{2} (x))

وسٌع:

- 2 + 2 sin^{2} (x)

- 2 (1 - sin^{2} (x))

a (b - c) = ab - a c

: افتح أقواس بالاستعانة بـ

a = - 2, b = 1, c = sin^{2} (x)

= - 2 \cdot 1 - (- 2) sin^{2} (x)

فعّل قوانين سالب-موجب

- (- a) = a

= - 2 \cdot 1 + 2 sin^{2} (x)

2 \cdot 1 = 2 :

اضرب الأعداد

= - 2 + 2 sin^{2} (x)

= 3 - 2 + 2 sin^{2} (x) - 4 sin^{2} (x)

3 - 2 + 2 sin^{2} (x) - 4 sin^{2} (x)

بسّط:

- 2 sin^{2} (x) + 1

3 - 2 + 2 sin^{2} (x) - 4 sin^{2} (x)

2 sin^{2} (x) - 4 sin^{2} (x) = - 2 sin^{2} (x) :

اجمع العناصر المتشابهة

= 3 - 2 - 2 sin^{2} (x)

3 - 2 = 1 :

اطرح الأعداد

= - 2 sin^{2} (x) + 1

= - 2 sin^{2} (x) + 1

= - 2 sin^{2} (x) + 1

1 - 2 sin^{2} (x) = 0

بالاستعانة بطريقة التعويض

1 - 2 sin^{2} (x) = 0

sin (x) = u :

على افتراض أنّ

1 - 2 u^{2} = 0

1 - 2 u^{2} = 0 : u = \frac{1}{2}, u = - \frac{1}{2}

1 - 2 u^{2} = 0

انقل

1

إلى الجانب الأيمن

1 - 2 u^{2} = 0

من الطرفين

1

اطرح

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

بسّط

- 2 u^{2} = - 1

- 2 u^{2} = - 1

- 2

اقسم الطرفين على

- 2 u^{2} = - 1

- 2

اقسم الطرفين على

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

بسّط

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

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

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

الحلول هي

x^{2} = f (a)

لـ

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

u = sin (x)

استبدل مجددًا

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

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

sin (x) = \frac{1}{2} : x = \frac{π}{4} + 2 πn, x = \frac{3 π}{4} + 2 πn

sin (x) = \frac{1}{2}

sin (x) = \frac{1}{2} :

حلول عامّة لـ

sin (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} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 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} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

x = \frac{π}{4} + 2 πn, x = \frac{3 π}{4} + 2 πn

x = \frac{π}{4} + 2 πn, x = \frac{3 π}{4} + 2 πn

sin (x) = - \frac{1}{2} : x = \frac{5 π}{4} + 2 πn, x = \frac{7 π}{4} + 2 πn

sin (x) = - \frac{1}{2}

sin (x) = - \frac{1}{2} :

حلول عامّة لـ

sin (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} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 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} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

x = \frac{5 π}{4} + 2 πn, x = \frac{7 π}{4} + 2 πn

x = \frac{5 π}{4} + 2 πn, x = \frac{7 π}{4} + 2 πn

وحّد الحلول

x = \frac{π}{4} + 2 πn, x = \frac{3 π}{4} + 2 πn, x = \frac{5 π}{4} + 2 πn, x = \frac{7 π}{4} + 2 πn

رسم

أمثلة شائعة

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sin^2(x)+sin(x)=-cos^2(x)

sin^{2} (x) + sin (x) = - cos^{2} (x)

arctan(x)=arccos(3/4)

arctan (x) = arccos (\frac{3}{4})

tan^2(θ)+7tan(θ)+9=0

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