NIMCET 2017 — Mathematics PYQ
NIMCET | Mathematics | 2017The maximum value of 4sin2x+3cos2x+sin2x+cos2x is
Choose the correct answer:
- A.
4
- B.
3+2
- C.
9
- D.
4+2
4+2
Explanation
Concept:
sin2x+cos2x=1
Calculation:
Let, f(x)=4sin2x+3cos2x+sin2x+cos2x
f(x)=4sin2x+3(1−sin2x)+sin2x+cos2x
=4sin2x+3−3sin2x+sin2x+cos2x
=sin2x+3+sin2x+cos2x
=sin2x+3+2[21sin2x+cos2x⋅21]
=3+sin2x+2sin(4π+2x)
=3+1+2(1)
(Max value of sin2x=1 and sin(4π+2x)=1)
So the maximum value of
4sin2x+3cos2x+sin2x+cos2x
is 4+2.
Hence, option (4) is correct.
Explanation
Concept:
sin2x+cos2x=1
Calculation:
Let, f(x)=4sin2x+3cos2x+sin2x+cos2x
f(x)=4sin2x+3(1−sin2x)+sin2x+cos2x
=4sin2x+3−3sin2x+sin2x+cos2x
=sin2x+3+sin2x+cos2x
=sin2x+3+2[21sin2x+cos2x⋅21]
=3+sin2x+2sin(4π+2x)
=3+1+2(1)
(Max value of sin2x=1 and sin(4π+2x)=1)
So the maximum value of
4sin2x+3cos2x+sin2x+cos2x
is 4+2.
Hence, option (4) is correct.

