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The solution o the equation cos^2theta+s...

The solution o the equation `cos^2theta+sintheta+1=0` lies in the interval `(-pi//4,pi//4)` b. `(pi//4,3pi//4)` c. `(3pi//4,5pi//4)` d. `(5pi//4,7pi//4)`

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We have, `cos^2theta+sintheta+1=0`
⟹`1−sin^2theta+sintheta+1=0`
⟹` (1−sintheta)(1+sintheta)+(1+sintheta)=0`
⟹` (1−sintheta+1)(1+sintheta)=0`
⟹`sintheta=−1 `
⟹`theta=3π/2`
∴`theta` lies in the interval `((5π)/4​,(7π)/4​)`
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