NIMCET 2012 — Mathematics PYQ
NIMCET | Mathematics | 2012If sin2x=1−sinx, then cos4x+cos2x is equal to:
Choose the correct answer:
- A.
0
- B.
1
(Correct Answer) - C.
32
- D.
−1
1
Explanation
1. Given Equation:
Rearrange the equation:
2. Using Identity:
We know the fundamental trigonometric identity: cos2x=1−sin2x.
Substituting this into the rearranged equation:
3. Squaring both sides:
To find the value of cos4x, square both sides of the relation sinx=cos2x:
4. Evaluating the Expression:
The expression we need to find is cos4x+cos2x.
Substitute cos4x=sin2x and cos2x=sinx (from the steps above):
5. Final Substitution:
From the very first rearranged given equation (sinx=1−sin2x), we can see that:
Therefore:
Correct Option:
(b) 1
Explanation
1. Given Equation:
Rearrange the equation:
2. Using Identity:
We know the fundamental trigonometric identity: cos2x=1−sin2x.
Substituting this into the rearranged equation:
3. Squaring both sides:
To find the value of cos4x, square both sides of the relation sinx=cos2x:
4. Evaluating the Expression:
The expression we need to find is cos4x+cos2x.
Substitute cos4x=sin2x and cos2x=sinx (from the steps above):
5. Final Substitution:
From the very first rearranged given equation (sinx=1−sin2x), we can see that:
Therefore:
Correct Option:
(b) 1

