CrackMath Question...please help!

[YourDentition]

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Is there a quick way to solve this?
Thanks a lot!

 

[mashimlro]

Pi=180 degree, so plug in; then you get cos 27270.
360 * 75 (circle/rotate 75 times, u know "all, sin, tan, cos graph, right?") = 27000
so, cos 27270 = cos (27270-27000) = cos 270

cos 270 (like cos 90) = 0

I hope it helps 😀

 

[Murl]

Did you upgrade and get the videos where the guy shows how to do the problems?

 

[Naijaba]

Cosine is a periodic function with a period of 2pi.

cos(pi + 301pi/2) = cos(pi + pi/2 + 300pi/2) = cos(pi + pi/2 + 150pi) = cos(pi + pi/2 + 2pi*75)

Here's where we apply the identity that cos(x + 2pi*n) = cos(x) if n is an integer:

cos(pi + pi/2 + 2pi*75) = cos(pi + pi/2) = cos(3pi/2)

cos(3pi/2) = 0 if you remember the unit circle from trigonometry.