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Byju's Answer
Standard XII
Mathematics
Range of Trigonometric Expressions
If sin A +sin...
Question
If
sin
A
+
sin
2
A
=
2
,
then the value of
cos
A
+
cos
2
A
+
cos
4
A
is
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Solution
sin
A
+
sin
2
A
=
2
⇒
sin
2
A
+
sin
A
−
2
=
0
⇒
(
sin
A
+
2
)
(
sin
A
−
1
)
=
0
⇒
sin
A
=
1
(
∵
sin
A
∈
[
−
1
,
1
]
)
⇒
cos
A
=
√
1
−
sin
2
A
=
0
Therefore,
cos
A
+
cos
2
A
+
cos
4
A
=
0
Suggest Corrections
0
Similar questions
Q.
If sin A + sin
2
A = 1, then the value of cos
2
A + cos
4
A is
(a) 2
(b) 1
(c) −2
(d) 0