MATHEMATICS HIGH SCHOOL

Which of the following is not equivalent to cos pi over 5 1. Cos negative pi over 5 2. Cos 9pi over 5 3. Cos 4 pi over 5 4. Cos 11 pi over 5

Answers

Answer 1

Answer:

The expression that is not equivalent to $\cos ((\pi)/(5))$ is:

3. $\cos((4\pi)/(5))$

Step-by-step explanation:

We are asked to find which of the expression is not equivalent to:

$\cos ((\pi)/(5))$

$\cos((-\pi)/(5))$

We know that:

$\cos(-\theta)=\cos(\theta)$

Hence, we get:

$\cos((-\pi)/(5))=\cos((\pi)/(5))$

Hence, option: 1 is incorrect.

$\cos((9\pi)/(5))$

We know that:

$\cos((9\pi)/(5))=\cos( 2\pi-(\pi)/(5))$

As we know that:

$\cos(2\pi-\theta)=\cos(\theta)$

Hence, we have:

$\cos((9\pi)/(5))=\cos((\pi)/(5))$

Hence, option: 2 is incorrect.

$\cos((11\pi)/(5))$

We know that:

$\cos((11\pi)/(5))=\cos( 2\pi+(\pi)/(5))$

As we know that:

$\cos(2\pi+\theta)=\cos(\theta)$

Hence, we have:

$\cos((11\pi)/(5))=\cos((\pi)/(5))$

Hence, option: 4 is incorrect.

$\cos((4\pi)/(5))$

We know that:

$\cos((4\pi)/(5))=\cos(\pi-(\pi)/(5))$

As we know that:

$\cos(\pi-\theta)=-\cos(\theta)$

Hence, we have:

$\cos((4\pi)/(5))=-\cos((\pi)/(5))\neq \cos ((\pi)/(5))$

Hence, option: 3 is the answer.

Answer 2

Answer: What is cos if u tell me i can answer

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Answers

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Answers

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Answer:

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Answers

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Step-by-step explanation:

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Answers

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Answer:

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Step-by-step explanation:

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