Question

1
10.
cosA.cos (60 + A).cos (60 - A) = COS 3A and hence deduce that co.20.0
40.0000380
tanA. tan (60+A) tan (60-A) = tan3A and hence deduce that tan20 tan40 tan60tan SV = 3
II.
12​

Answer 1

Answer:

cosAcos(60−A)cos(60+A)=

4

cos3A

cos(x−y)cos(x+y)=cos

2

y−sin

2

x

cos3x=4cos

3

x−3cosx

cosAcos(60−A)cos(60+A)

=cosA(cos

2

(A)−sin

2

60)

=cosA(cos

2

A−

4

3

)

=

4

4cos

3

A−3cosA

=

4

cos3A