- #1

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Why 1 divided by cos(pi/4)=cos(-pi/4)?

Is it wrong to say 1/cos(pi/4)=sec(pi/4)?

Thanks

Is it wrong to say 1/cos(pi/4)=sec(pi/4)?

Thanks

- Thread starter ryanuser
- Start date

- #1

- 74

- 0

Why 1 divided by cos(pi/4)=cos(-pi/4)?

Is it wrong to say 1/cos(pi/4)=sec(pi/4)?

Thanks

Is it wrong to say 1/cos(pi/4)=sec(pi/4)?

Thanks

- #2

Buzz Bloom

Gold Member

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Hi ryan:

I hope this is helpful.

BTW: The title of the thread does not match your question. The inverse of the cos is the arccos, which is not the same as the reciprocal, 1/cos.

Regards,

Buzz

Is it wrong to say 1/cos(pi/4)=sec(pi/4)?

1/cos(pi/4)=sec(pi/4) is correct.Why 1 divided by cos(pi/4)=cos(-pi/4)?

I think you are asking: Why is the following correct?1/cos(pi/4) = 1/cos(-pi/4)?

If this is what you are asking, the reason that is correct is becausecos(pi/4) = cos(-pi/4),

which is becausethe cos function is symmetrical,

and becausethe reciprocal of two equal numbers will be equal.

I hope this is helpful.

BTW: The title of the thread does not match your question. The inverse of the cos is the arccos, which is not the same as the reciprocal, 1/cos.

Regards,

Buzz

Last edited:

- #3

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Thanks you

- #4

Mark44

Mentor

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The thread title is now "Reciprocal of cos".BTW: The title of the thread does not match your question. The inverse of the cos is the arccos, which is not the same as the reciprocal, 1/cos.

- #5

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1/cos(pi/4) is not equal to cos(-pi/4). Cos(-pi/4) is equal to cos(pi/4). It is because cos function is an even function and it produces same answer to negative and positive values. I can give you a simple reason that 0 and 2pi is same in angles and 0-pi/4 is same as 2pi-pi/4 if you see graph paper, rotate a line from positive X-axis in anti-clock wise direction it lies in fourth quadrant. Now, you see x co-ordinate is positive and hypotenuse is length so it's positive. Hence, base/hypotenuse is positive.

I hope this one helps and if any other query regarding my answer please ask.

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