Grade 11Trigonometry
If 2 cosθ = a +
1
a
, prove that 2 cos 2θ = a
2 +
1
a
2
and
2 cos 3θ = a
3 +
1
a
3
If 2 cosθ = a +
1
a
, prove that 2 cos 2θ = a
2 +
1
a
2
and
2 cos 3θ = a
3 +
1
a
3
1
a
, prove that 2 cos 2θ = a
2 +
1
a
2
and
2 cos 3θ = a
3 +
1
a
3
