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شائع علم المثلثات >

prove 1-(-cos(x))^2=1+cos^2(x)

الحلّ

prove

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

الحلّ

خطأ

خطوات الحلّ

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

لا يتساوى الطرفان

x = 0

عوّض

, 1 - (- cos (x))^{2} = 1 + cos^{2} (x)

في

1 - (- cos (0))^{2} = 0

1 - (- cos (0))^{2}

استخدم المتطابقة الأساسيّة التالية:

cos (0) = 1

cos (0)

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}

= 1

= 1 - (- 1)^{2}

1 - (- 1)^{2}

بسّط:

0

1 - (- 1)^{2}

(- 1)^{2} = 1

(- 1)^{2}

زوجيّ n

إذا تحقّق أنّ

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

:فعّل قانون القوى

(- 1)^{2} = 1^{2}

= 1^{2}

1^{a} = 1

فعّل القانون

= 1

= 1 - 1

1 - 1 = 0 :

اطرح الأعداد

= 0

= 0

1 + cos^{2} (0) = 2

1 + cos^{2} (0)

استخدم المتطابقة الأساسيّة التالية:

cos (0) = 1

cos (0)

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}

= 1

= 1 + 1^{2}

بسّط

= 2

لا يتساوى الطرفان

\Rightarrow خطأ

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