162 Higher Engineering Mathematics
- cosAsinB=
1
2
[sin(A+B)−sin(A−B)]
⎡
⎢
⎣
coshθcoshφ=
1
2
[sinh(θ+φ)
−sinh(θ−φ)]
⎤
⎥
⎦
- sin^3 A=
3
4
sinA−
1
4
sin3A
[
sinh^3 θ=
1
4
sinh3θ−
3
4
sinhθ
]
- cot^2 A(sec^2 A− 1 )= 1
[coth^2 θ( 1 −sech^2 θ)=1]
162 Higher Engineering Mathematics
1
2
[sin(A+B)−sin(A−B)]
⎡
⎢
⎣
coshθcoshφ=
1
2
[sinh(θ+φ)
−sinh(θ−φ)]
⎤
⎥
⎦
3
4
sinA−
1
4
sin3A
[
sinh^3 θ=
1
4
sinh3θ−
3
4
sinhθ
]