次の式を
r cos ( θ α + ) の形に変形せよ。
(1)
sin θ + cos θ 2 cos 1 sin 1
2 2
θ θ
= ⋅ + ⋅
2 cos cos sin sin
4 4
π π
θ θ
= +
2 cos
4 θ π
= −
(2)
sin θ − 3 cos θ 3 1
2 cos sin
2 2
θ θ
= ⋅ − + ⋅
5 5
2 cos cos sin sin
6 6
θ π θ π
= +
2 cos 5
θ 6 π
= −
(3)
5sin θ + 12 cos θ 12 5
13 cos sin
13 13
θ θ
= ⋅ + ⋅
( )
13cos θ β
= −
（β
はcos 12
β = 13
かつ5
sin β = 13
を満たす角）(4)
cos cos
3
θ + θ + π cos cos cos sin sin
3 3
π π
θ θ θ
= + −
3 3
cos sin
2 θ 2 θ
= −
3 1
3 cos sin
2 2
θ θ
= ⋅ + ⋅ −
3 cos cos sin sin
6 6
π π
θ θ
= − + −
3 cos
6 θ π
= − − 3 cos 6 θ π
= +
８３．三角関数の合成②(1)
