@ find the value of 2cos sqare 15-1
Answers
Answered by
1
Step-by-step explanation:
To find cos
2
45
o
−sin
2
15
o
We know that, cos2θ=2cos
2
θ−1⟹cos
2
θ=
2
1+cos2θ
And cos2θ=1−2sin
2
θ⟹sin
2
θ=
2
1−cos2θ
∴cos
2
45
o
=
2
1+cos(2×45)
=
2
1+cos90
o
=
2
1+0
=
2
1
Also, ∴sin
2
15
o
=
2
1−cos(2×15)
=
2
1−cos30
o
=
2
1−
2
3
=
2
1
−
4
3
Then we get,
cos
2
45
o
−sin
2
15
o
=
2
1
−
2
1
+
4
3
=
4
3
Hence, cos
2
45
o
−sin
2
15
o
=
4
3
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