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KCET 2025 Math Paper

Question : 5 of 60

Marks: +1, -0

Which of the following is not correct?

Solution:

Let's check each identity:

Option A:

\cos 5\pi = \cos (\pi + 4\pi) = -1, \; \; \cos 4\pi = 1

These are not equal, so A is false.

Option B:

\sin\; 2\pi = 0, \; \; \sin\; (-2\pi) = -\sin\; 2\pi = 0

Option C:

\sin\; 4\pi = 0, \; \; \sin\; 6\pi = 0

Option D:

\tan 45^{\circ} = 1, \; \; \tan (-315^{\circ}) = \tan (45^{\circ}) = 1

Only Option A fails, so the incorrect statement is Option A.

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