find the value of cos(40⁰+theta)cos(10⁰+theta) + sin(40⁰+theta)sin(10⁰+theta)
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sin(40
0
+θ)cos(10
0
+θ)−cos(40
0
+θ)sin(10
0
+θ)=sinAcosB−cosAsinB,
Where (40
0
+θ)=A and (10
0
+θ)=B
sin(A−B)=sin{(40
0
+θ)−(10
0
+θ)}=sin30
0
=
2
1
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