The cotangent function is defined as the ratio between cosine and sine of a given angle, i.e.

Since you can't have zero at the denominator, the cotangent function is not defined when the sine is zero.
Let's look at your option:
, so the cotangent is defined here
, so the cotangent is not defined here
, so the cotangent is defined here
, so the cotangent is defined here
Answer:
18225
Step-by-step explanation:
: Let y = f(x) = x^1/3
Then dy = 1/3*x^(−2/3) dx
Since f(64) = 4.
We take x = 64 and dx = ∆x = 1
This gives dy = 1/3*(64)^(−2/3)* (1) = 1/48
∴65^(1/3) = f(64 + 1) ≈ f(64) + dy = 4 + 1/48 ≈ 4.021 <span>
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