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شائع علم المثلثات >

sin(x+pi/4)=sqrt(2)cos(x+pi/4)

الحلّ

sin (x + \frac{π}{4}) = 2 cos (x + \frac{π}{4})

الحلّ

x = \frac{0.33983 \dots}{2} + πn

درجات

x = 9.73561 \dots^{\circ} + 18 0^{\circ} n

خطوات الحلّ

sin (x + \frac{π}{4}) = 2 cos (x + \frac{π}{4})

ربّع الطرفين

sin^{2} (x + \frac{π}{4}) = (2 cos (x + \frac{π}{4}))^{2}

Rewrite using trig identities

sin^{2} (x + \frac{π}{4}) = (2 cos (x + \frac{π}{4}))^{2}

Rewrite using trig identities

sin (x + \frac{π}{4})

sin (s + t) = sin (s) cos (t) + cos (s) sin (t)

:فعّل متطابقة الجمع لزوايا

= sin (x) cos (\frac{π}{4}) + cos (x) sin (\frac{π}{4})

sin (x) cos (\frac{π}{4}) + cos (x) sin (\frac{π}{4})

بسّط:

\frac{2 sin ( x ) + 2 cos ( x )}{2}

sin (x) cos (\frac{π}{4}) + cos (x) sin (\frac{π}{4})

sin (x) cos (\frac{π}{4}) = \frac{2 sin ( x )}{2}

sin (x) cos (\frac{π}{4})

cos (\frac{π}{4})

بسّط:

\frac{2}{2}

cos (\frac{π}{4})

استخدم المتطابقة الأساسيّة التالية:

cos (\frac{π}{4}) = \frac{2}{2}

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

= \frac{2}{2}

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

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

:اضرب كسور

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

cos (x) sin (\frac{π}{4}) = \frac{2 cos ( x )}{2}

cos (x) sin (\frac{π}{4})

sin (\frac{π}{4})

بسّط:

\frac{2}{2}

sin (\frac{π}{4})

استخدم المتطابقة الأساسيّة التالية:

sin (\frac{π}{4}) = \frac{2}{2}

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}

= \frac{2}{2}

= \frac{2}{2} cos (x)

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

:اضرب كسور

= \frac{2 cos ( x )}{2}

= \frac{2 sin ( x )}{2} + \frac{2 cos ( x )}{2}

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

فعّل القانون

= \frac{2 sin ( x ) + 2 cos ( x )}{2}

= \frac{2 sin ( x ) + 2 cos ( x )}{2}

cos (s + t) = cos (s) cos (t) - sin (s) sin (t)

:فعّل متطابقة الجمع لزوايا

= cos (x) cos (\frac{π}{4}) - sin (x) sin (\frac{π}{4})

cos (x) cos (\frac{π}{4}) - sin (x) sin (\frac{π}{4})

بسّط:

\frac{2 cos ( x ) - 2 sin ( x )}{2}

cos (x) cos (\frac{π}{4}) - sin (x) sin (\frac{π}{4})

cos (x) cos (\frac{π}{4}) = \frac{2 cos ( x )}{2}

cos (x) cos (\frac{π}{4})

cos (\frac{π}{4})

بسّط:

\frac{2}{2}

cos (\frac{π}{4})

استخدم المتطابقة الأساسيّة التالية:

cos (\frac{π}{4}) = \frac{2}{2}

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

= \frac{2}{2}

= \frac{2}{2} cos (x)

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

:اضرب كسور

= \frac{2 cos ( x )}{2}

sin (x) sin (\frac{π}{4}) = \frac{2 sin ( x )}{2}

sin (x) sin (\frac{π}{4})

sin (\frac{π}{4})

بسّط:

\frac{2}{2}

sin (\frac{π}{4})

استخدم المتطابقة الأساسيّة التالية:

sin (\frac{π}{4}) = \frac{2}{2}

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}

= \frac{2}{2}

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

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

:اضرب كسور

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

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

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

فعّل القانون

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

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

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

(\frac{2 sin ( x ) + 2 cos ( x )}{2})^{2}

بسّط:

\frac{( sin ( x ) + cos ( x ) ) ^{2}}{2}

(\frac{2 sin ( x ) + 2 cos ( x )}{2})^{2}

\frac{2 sin ( x ) + 2 cos ( x )}{2} = \frac{sin ( x ) + cos ( x )}{2}

\frac{2 sin ( x ) + 2 cos ( x )}{2}

2

قم باخراج العامل المشترك

= \frac{2 ( sin ( x ) + cos ( x ) )}{2}

\frac{2 ( sin ( x ) + cos ( x ) )}{2}

اختزل:

\frac{sin ( x ) + cos ( x )}{2}

\frac{2 ( sin ( x ) + cos ( x ) )}{2}

n a = a^{\frac{1}{n}}

:فعْل قانون الجذور

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

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

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

:فعّل قانون القوى

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

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

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

اطرح الأعداد

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

a^{\frac{1}{n}} = n a

:فعْل قانون الجذور

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

= \frac{sin ( x ) + cos ( x )}{2}

= \frac{sin ( x ) + cos ( x )}{2}

= (\frac{sin ( x ) + cos ( x )}{2})^{2}

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

:فعّل قانون القوى

= \frac{( sin ( x ) + cos ( x ) ) ^{2}}{( 2 ) ^{2}}

(2)^{2} : 2

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

:فعْل قانون الجذور

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

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

:فعّل قانون القوى

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

\frac{1}{2} \cdot 2 = 1

\frac{1}{2} \cdot 2

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

:اضرب كسور

= \frac{1 \cdot 2}{2}

2 :

إلغ العوامل المشتركة

= 1

= 2

= \frac{( sin ( x ) + cos ( x ) ) ^{2}}{2}

(2 \frac{2 cos ( x ) - 2 sin ( x )}{2})^{2}

بسّط:

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

(2 \frac{2 cos ( x ) - 2 sin ( x )}{2})^{2}

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

\frac{2 cos ( x ) - 2 sin ( x )}{2}

2

قم باخراج العامل المشترك

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

\frac{2 ( cos ( x ) - sin ( x ) )}{2}

اختزل:

\frac{cos ( x ) - sin ( x )}{2}

\frac{2 ( cos ( x ) - sin ( x ) )}{2}

n a = a^{\frac{1}{n}}

:فعْل قانون الجذور

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

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

\frac{x ^{a}}{x ^{b}} = \frac{1}{x ^{b - a}}

:فعّل قانون القوى

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

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

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

اطرح الأعداد

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

a^{\frac{1}{n}} = n a

:فعْل قانون الجذور

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

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

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

= (2 \frac{cos ( x ) - sin ( x )}{2})^{2}

2 \frac{cos ( x ) - sin ( x )}{2}

اضرب بـ:

cos (x) - sin (x)

2 \frac{cos ( x ) - sin ( x )}{2}

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

:اضرب كسور

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

2 :

إلغ العوامل المشتركة

= cos (x) - sin (x)

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

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

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

من الطرفين

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

اطرح

\frac{- sin ^{2} ( x ) + 6 cos ( x ) sin ( x ) - cos ^{2} ( x )}{2} = 0

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

- sin^{2} (x) + 6 cos (x) sin (x) - cos^{2} (x) = 0

Rewrite using trig identities

6 cos (x) sin (x) - 1

2 sin (x) cos (x) = sin (2 x)

:فعّل متطابقة الزاوية المضاعفة

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

= - 1 + 6 \cdot \frac{sin ( 2 x )}{2}

- 1 + 6 \cdot \frac{sin ( 2 x )}{2} = 0

6 \cdot \frac{sin ( 2 x )}{2} = 3 sin (2 x)

6 \cdot \frac{sin ( 2 x )}{2}

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

:اضرب كسور

= \frac{sin ( 2 x ) \cdot 6}{2}

\frac{6}{2} = 3 :

اقسم الأعداد

= 3 sin (2 x)

- 1 + 3 sin (2 x) = 0

انقل

1

إلى الجانب الأيمن

- 1 + 3 sin (2 x) = 0

للطرفين

1

أضف

- 1 + 3 sin (2 x) + 1 = 0 + 1

بسّط

3 sin (2 x) = 1

3 sin (2 x) = 1

3

اقسم الطرفين على

3 sin (2 x) = 1

3

اقسم الطرفين على

\frac{3 sin ( 2 x )}{3} = \frac{1}{3}

بسّط

sin (2 x) = \frac{1}{3}

sin (2 x) = \frac{1}{3}

Apply trig inverse properties

sin (2 x) = \frac{1}{3}

sin (2 x) = \frac{1}{3} :

حلول عامّة لـ

sin (x) = a \Rightarrow x = arcsin (a) + 2 πn, x = π - arcsin (a) + 2 πn

2 x = arcsin (\frac{1}{3}) + 2 πn, 2 x = π - arcsin (\frac{1}{3}) + 2 πn

2 x = arcsin (\frac{1}{3}) + 2 πn, 2 x = π - arcsin (\frac{1}{3}) + 2 πn

2 x = arcsin (\frac{1}{3}) + 2 πn

حلّ:

x = \frac{arcsin ( \frac{1}{3} )}{2} + πn

2 x = arcsin (\frac{1}{3}) + 2 πn

2

اقسم الطرفين على

2 x = arcsin (\frac{1}{3}) + 2 πn

2

اقسم الطرفين على

\frac{2 x}{2} = \frac{arcsin ( \frac{1}{3} )}{2} + \frac{2 πn}{2}

بسّط

x = \frac{arcsin ( \frac{1}{3} )}{2} + πn

x = \frac{arcsin ( \frac{1}{3} )}{2} + πn

2 x = π - arcsin (\frac{1}{3}) + 2 πn

حلّ:

x = \frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + πn

2 x = π - arcsin (\frac{1}{3}) + 2 πn

2

اقسم الطرفين على

2 x = π - arcsin (\frac{1}{3}) + 2 πn

2

اقسم الطرفين على

\frac{2 x}{2} = \frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + \frac{2 πn}{2}

بسّط

x = \frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + πn

x = \frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + πn

x = \frac{arcsin ( \frac{1}{3} )}{2} + πn, x = \frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + πn

تأكّد من صحّة الحلول عن طريق تعويضها في المعادلة الأصليّة

للتحقّق من دقّة الحلول

sin (x + \frac{π}{4}) = 2 cos (x + \frac{π}{4})

عوّض الحلول في

إلغي الحلول التي تعطي قضيّة كذب

\frac{arcsin ( \frac{1}{3} )}{2} + πn

افحص الحل:

صحيح

\frac{arcsin ( \frac{1}{3} )}{2} + πn

n = 1

استبدل

\frac{arcsin ( \frac{1}{3} )}{2} + π 1

x = \frac{arcsin ( \frac{1}{3} )}{2} + π 1

عوّض

, sin (x + \frac{π}{4}) = 2 cos (x + \frac{π}{4})

في

sin (\frac{arcsin ( \frac{1}{3} )}{2} + π 1 + \frac{π}{4}) = 2 cos (\frac{arcsin ( \frac{1}{3} )}{2} + π 1 + \frac{π}{4})

بسّط

- 0.81649 \dots = - 0.81649 \dots

\Rightarrow صحيح

\frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + πn

افحص الحل:

خطأ

\frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + πn

n = 1

استبدل

\frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + π 1

x = \frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + π 1

عوّض

, sin (x + \frac{π}{4}) = 2 cos (x + \frac{π}{4})

في

sin (\frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + π 1 + \frac{π}{4}) = 2 cos (\frac{π}{2} - \frac{arcsin ( \frac{1}{3} )}{2} + π 1 + \frac{π}{4})

بسّط

- 0.81649 \dots = 0.81649 \dots

\Rightarrow خطأ

x = \frac{arcsin ( \frac{1}{3} )}{2} + πn

أظهر الحلّ بالتمثيل العشريّ

x = \frac{0.33983 \dots}{2} + πn

رسم

أمثلة شائعة

5=7cos(pi/3 t)

5 = 7 cos (\frac{π}{3} t)

6cos^2(x)-4=0

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

csc(x)=3.5

csc (x) = 3.5

sin(x)=0,sin(x)=0

sin (x) = 0, sin (x) = 0

cos(x)=-7/9 , pi/2 <x<pi

cos (x) = - \frac{7}{9}, \frac{π}{2} < x < π