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شائع علم المثلثات >

1/(sin(2x))< 1/(sin(x)),0<= x<= pi

الحلّ

\frac{1}{sin ( 2 x )} < \frac{1}{sin ( x )}, 0 \leq x \leq π

الحلّ

0 < x < \frac{π}{3} or \frac{π}{2} < x < π

تدوين الفاصل الزمني

(0, \frac{π}{3}) \cup (\frac{π}{2}, π)

عشري

0 < x < 1.04719 \dots or 1.57079 \dots < x < 3.14159 \dots

خطوات الحلّ

\frac{1}{sin ( 2 x )} < \frac{1}{sin ( x )}, 0 \leq x \leq π

انقل

\frac{1}{sin ( x )}

إلى الجانب الأيسر

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

من الطرفين

\frac{1}{sin ( x )}

اطرح

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

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

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

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

:استخدم المتطابقة التالية

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

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

بسّط:

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

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

2 cos (x) sin (x), sin (x)

المضاعف المشترك الأصغر لـ:

2 cos (x) sin (x)

2 cos (x) sin (x), sin (x)

Lowest Common Multiplier (LCM)

Compute an expression comprised of factors that appear either in

2 cos (x) sin (x)

sin (x)

= 2 cos (x) sin (x)

اكتب مجددًا الكسور بحيث يكون المقام مشترك

2 cos (x) sin (x)

اضرب كل بسط ومقام بتعبير الذي يؤدّي إلى مقام مشترك

For

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

multiply the denominator and numerator by

2 cos (x)

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

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

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

:بما أنّ المقامات متساوية، اجمع البسوط

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

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

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

دوريّة:

2 π

The compound periodicity of the sum of periodic functions is the least common multiplier of the periods

\frac{1}{2 cos ( x ) sin ( x )}, \frac{1}{sin ( x )}

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

دوريّة:

π

:

مركّبة من الدوالّ والدوريّات التالية

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

2 π

مع دوريّات

cos (x)

:

الدوريّة المركّبة للدالّة هي

π

\frac{1}{sin ( x )}

دوريّة:

2 π

a sin (b x \pm c) \pm d = \frac{sin دوريّة}{∣ b ∣}

دوريّة ال

2 π

هي

sin (x)

دوريّة

= \frac{2 π}{∣ 1 ∣}

بسّط

= 2 π

Combine periods:

π, 2 π

= 2 π

Find the zeroes and undifined points of

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

for

0 \leq x < 2 π

To find the zeroes, set the inequality to zero

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

\frac{1 - 2 cos ( x )}{2 cos ( x ) sin ( x )} = 0, 0 \leq x < 2 π : x = \frac{π}{3}, x = \frac{5 π}{3}

\frac{1 - 2 cos ( x )}{2 cos ( x ) sin ( x )} = 0, 0 \leq x < 2 π

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

1 - 2 cos (x) = 0

انقل

1

إلى الجانب الأيمن

1 - 2 cos (x) = 0

من الطرفين

1

اطرح

1 - 2 cos (x) - 1 = 0 - 1

بسّط

- 2 cos (x) = - 1

- 2 cos (x) = - 1

- 2

اقسم الطرفين على

- 2 cos (x) = - 1

- 2

اقسم الطرفين على

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

بسّط

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

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

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

حلول عامّة لـ

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}

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

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

0 \leq x < 2 π :

حلول للمدى

x = \frac{π}{3}, x = \frac{5 π}{3}

Find the undefined points:

x = \frac{π}{2}, x = \frac{3 π}{2}, x = 0, x = π

Find the zeros of the denominator

2 cos (x) sin (x) = 0

حلّ كل جزء على حدة

cos (x) = 0 or sin (x) = 0

cos (x) = 0, 0 \leq x < 2 π : x = \frac{π}{2}, x = \frac{3 π}{2}

cos (x) = 0, 0 \leq x < 2 π

cos (x) = 0 :

حلول عامّة لـ

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}

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

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

0 \leq x < 2 π :

حلول للمدى

x = \frac{π}{2}, x = \frac{3 π}{2}

sin (x) = 0, 0 \leq x < 2 π : x = 0, x = π

sin (x) = 0, 0 \leq x < 2 π

sin (x) = 0 :

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 = 0 + 2 πn, x = π + 2 πn

x = 0 + 2 πn, x = π + 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, x = π + 2 πn

0 \leq x < 2 π :

حلول للمدى

x = 0, x = π

وحّد الحلول

x = \frac{π}{2}, x = \frac{3 π}{2}, x = 0, x = π

0, \frac{π}{3}, \frac{π}{2}, π, \frac{3 π}{2}, \frac{5 π}{3}

ميّز المقاطع المختلفة

0 < x < \frac{π}{3}, \frac{π}{3} < x < \frac{π}{2}, \frac{π}{2} < x < π, π < x < \frac{3 π}{2}, \frac{3 π}{2} < x < \frac{5 π}{3}, \frac{5 π}{3} < x < 2 π

لخّص في جدول

1 - 2 cos (x) cos (x) sin (x) \frac{1 - 2 c o s ( x )}{2 c o s ( x ) s i n ( x )} x = 0 - + 0 غير معرّف 0 < x < \frac{π}{3} - + + - x = \frac{π}{3} 0 + + 0 \frac{π}{3} < x < \frac{π}{2} + + + + x = \frac{π}{2} + 0 + غير معرّف \frac{π}{2} < x < π + - + - x = π + - 0 غير معرّف π < x < \frac{3 π}{2} + - - + x = \frac{3 π}{2} + 0 - غير معرّف \frac{3 π}{2} < x < \frac{5 π}{3} + + - - x = \frac{5 π}{3} 0 + - 0 \frac{5 π}{3} < x < 2 π - + - + x = 2 π - + 0 غير معرّف

< 0 :

ميّز المقاطع التي تحقّق الشرط

0 < x < \frac{π}{3} or \frac{π}{2} < x < π or \frac{3 π}{2} < x < \frac{5 π}{3}

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

استخدم دوريّة الـ

2 πn < x < \frac{π}{3} + 2 πn or \frac{π}{2} + 2 πn < x < π + 2 πn or \frac{3 π}{2} + 2 πn < x < \frac{5 π}{3} + 2 πn

وحّد المقاطع

2 πn < x < \frac{π}{3} + 2 πn or \frac{π}{2} + 2 πn < x < π + 2 πn or \frac{3 π}{2} + 2 πn < x < \frac{5 π}{3} + 2 πn and 0 \leq x \leq π

0 < x < \frac{π}{3} or \frac{π}{2} < x < π

رسم

أمثلة شائعة

2tan(2x)<= 3tan(x)

2 tan (2 x) \leq 3 tan (x)

1/((sin(x))^2)< 4/3 ,0<x< pi/(15)

\frac{1}{( sin ( x ) ) ^{2}} < \frac{4}{3}, 0 < x < \frac{π}{15}

cos^2(x)<sin^2(x)

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

sin(x-45)> 1/2 sqrt(3),0<= x<= 360

sin (x - 4 5^{\circ}) > \frac{1}{2} 3, 0^{\circ} \leq x \leq 36 0^{\circ}

2sin^2(x)>-1

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