I have a question that does not have anything to do with coding.

Question

So I'm learning about Sin, Cos, and Tan, but there is something that I do not understand at all.

So my question is, what does sin(25°) = -sin(25°) ????
I do understand the sin(25°) but the part that I don't understand is the -sin(25°)!

What does - sign behind the sin means??? I tried searching it at Google but I can't find a clear answer about it...

does the -sin(25°) means sin(-25°) or it can be both sin(25°) and sin(-25°)???

Sorry for the stupid question 😭🙏🏻.

Answer 1

Mirielle

Does the opposite you mean is like this (/)? or is it more like this (<)?

I'm trying to draw a circle with parenthese and a line in it.

And sorry for the bad english! I'm not a native.

Answer 2

brushing up on dusty trigonometry,
this also applies to cos and tan.

https://www.adelaide.edu.au/mathslearning/ua/media/36/useful-trig-identities.pdf

if you think about it, putting a negative in front of sin, cos or tan is basically flipping it along the x-axis, so that makes it equal to the corresponding sin, cos or tan of the negative angle.

so yes, sin(-x) is the same as -sin(x)

Answer 3

Is this the opposite you were talking about??

sin(25°) = -sin(25°)

Y
^
|
| *
| *
| *
| *
|-----------------------------> X
*
*
*
*

This is the best angle I can only make with keyboard

Answer 4

Theres something wrong in your initial assumptions here.

sin(25 degrees) is approximatly 0.4226. Obviously, 0.4 is not equal to -0.4. Instead, the actual general equation that you should be looking for is:

sin(x) = -sin(-x)

And in this case, sin(-25 degrees) does indeed approximate to -0.4226.

Source:
https://www.wolframalpha.com/input/?i=sin(x)

Answer 5

Mirielle and Jay Matthews, thank you for the answers 😭🙏🏻

Hope you guys a have a great day!

Answer 6

Best to go to Khan Academy, it is well explained and you will be able to practice the knowledge with exercises.
It is free, khanacademy.org you want to head to Math/Trigonometry.

Answer 7

Robert Butler, Bob_Li, and Marcus Bigtree

Sorry for the late reply!
I will try checking all the sources and I'll try checking at Khan Academy too. Thanks a lot for the explanation! Thank you so much.

Answer 8

I have no idea lol, x or y???