MCQ
Let f : R × R be a function defined by $ \text{f}(\text{x}) = \cos(2\text{x} + 5)$, then f is:
- Ainjective
- Bsurjective
- Cbijective
- DNone of these
Solution:
Given, $ \text{f}(\text{x}) = \cos(2\text{x} + 5)$
Period of $\text{f}(\text{x})=\frac{2\pi}{5}$
Since f(x) is a periodic function with period $\text{f}(\text{x})=\frac{2\pi}{5}$ so it is not injective.
The function f is not surjective also as its range [-1, 1] is a proper subset of its co-domain R.
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