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The number of roots of equation cos^(7)t...

The number of roots of equation `cos^(7)theta - sin^(4)theta = 1` that lie in the interval `[0,2pi]` is-

A

2

B

3

C

4

D

8

Text Solution

Verified by Experts

The correct Answer is:
A
`cos^(7)theta = 1 + sin^(4)theta ge 1` but `cos^(7) le 1`
so `cos theta = 1 , sin theta = 0`
`theta = 0, 2pi`
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