What is the value for Cos (90°+15°)
Answers
Answered by
1
cos
105
=
1
−
√
3
2
√
2
Explanation:
You can write
cos
(
105
)
as
cos
(
45
+
60
)
Now,
cos
(
A
+
B
)
=
cos
A
cos
B
−
sin
A
sin
B
So,
cos
(
105
)
=
cos
45
cos
60
−
sin
45
sin
60
=
(
1
√
2
)
⋅
(
1
2
)
−
(
1
√
2
)
(
√
3
2
)
=
1
−
√
3
2
√
2
Answered by
1
cos (A+B)
= cos A cos B - sin A sin B
Cos (90+15) = cos (45+60)
= cos 45 cos 60 - sin 45 sin 60
= 1/(2√2) - √3/√2
= (1-2√3)/2√2
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