Question

4. Which of the following relation is true? A) cos 4° cos 40 O cos 4º = cos 49 D) cos 4° 2 cos 40​

Answer 1

Step-by-step explanation:

Correct option is

B

2

1

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