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Standard X
Mathematics
Question
Evaluate:
cos
20
∘
cos
70
∘
−
sin
20
∘
sin
70
∘
Open in App
Solution
Verified by Toppr
cos
20
°
cos
70
°
−
sin
70
°
sin
20
°
=
0
⇒
cos
20
°
cos
70
°
−
sin
70
°
sin
20
°
=
cos
(
70
°
+
20
°
)
[
∵
cos
A
cos
B
−
sin
A
sin
B
=
cos
(
A
+
B
)
]
=
cos
90
°
=
0
Hence, the answer is solved.
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Similar Questions
Q1
Evaluate:
cos
20
∘
cos
70
∘
−
sin
20
∘
sin
70
∘
View Solution
Q2
Write the value of
sin
20
°
-
cos
20
°
sin
70
°
cos
70
°
.
View Solution
Q3
The value of
sin
20
∘
cos
70
∘
+
cos
20
∘
sin
70
∘
sin
23
∘
c
o
sec
23
∘
+
cos
23
∘
sec
23
∘
is
View Solution
Q4
Evaluate the following :
c
o
s
20
s
i
n
70
View Solution
Q5
Prove that:
(i) cos 10° cos 30° cos 50° cos 70° =
3
16
(ii) cos 40° cos 80° cos 160° =
-
1
8
(iii) sin 20° sin 40° sin 80° =
3
8
(iv) cos 20° cos 40° cos 80° =
1
8
(v) tan 20° tan 40° tan 60° tan 80° = 3
(vi) tan 20° tan 30° tan 40° tan 80° = 1
(vii) sin 10° sin 50° sin 60° sin 70° =
3
16
(viii) sin 20° sin 40° sin 60° sin 80° =
3
16
View Solution