Prove that 1 + cos 20 + sin2
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Answered by
1
Answer:
−
cos(20
0
)
1
=
sin(20
0
)cos(20
0
)
3
cos(20
0
)−sin(20
0
)
=
2sin(20
0
)cos(20
0
)
4[
2
3
cos(20
0
)−
2
sin(20)
0
]
[∵2sinAcosA=sin2A]
=
sin40
0
4(sin60
0
cos20
0
−cos60
0
sin20
)
=
sin40
0
4sin(60
0
−20
0
)
[∵sin(A−B)=sinAcosB−cosAsinB]
=
sin40
0
4sin40
0
=4
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