Asked by Raj
Find the value of cos(-225).
Answers
Answered by
Reiny
cos(-225°) is coterminal with cos 135°
By the CAST rule, cos 135° = -cos 45°
= -1/√2 or -√2/2
By the CAST rule, cos 135° = -cos 45°
= -1/√2 or -√2/2
Answered by
oobleck
cos(-x) = cos(x)
cos(x-180) = -cos(x)
See if that helps you.
Or, draw the triangle in standard position, and recall that
cos(x) = x/r
cos(x-180) = -cos(x)
See if that helps you.
Or, draw the triangle in standard position, and recall that
cos(x) = x/r
Answered by
Raj
Explain me in terms of unit circle.
Answered by
Reiny
Ok
Going either -225° or 135°, you would end up in the same position, right?
Now draw you 1 unit radius at 135 and sketch your right-angled triangle.
You have a right-angled triangle with a base and height of √2.
the value of x = -√2 and the the value of y is +√2
cos -225 = cos 135 = x/r = -√2/2
Going either -225° or 135°, you would end up in the same position, right?
Now draw you 1 unit radius at 135 and sketch your right-angled triangle.
You have a right-angled triangle with a base and height of √2.
the value of x = -√2 and the the value of y is +√2
cos -225 = cos 135 = x/r = -√2/2
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.