Question:
why we write cos(-x)=cos x
Answer:
Given cos(-x) can also be written as cos(0 - x)
Now apply formula
cos(A-B) = cosA * cosB + sinA * sinB
=> cos(0-x) = cos0 * cosx + sin0 * sinx
= 1 * cosx + 0 * sinx (cos0 = 1 and sin0 = 1)
= cosx
So cos(0 - x) = cos(-x) = cosx
Not what you are looking for? Go ahead and submit the question, we will get back to you.
