Higher Engineering Mathematics, Sixth Edition

162 Higher Engineering Mathematics

5. cosAsinB=

1

2

[sin(A+B)−sin(A−B)]

⎡

⎢

⎣

coshθcoshφ=

1

2

[sinh(θ+φ)

−sinh(θ−φ)]

⎤

⎥

⎦

6. sin^3 A=

3

4

sinA−

1

4

sin3A

[

sinh^3 θ=

1

4

sinh3θ−

3

4

sinhθ

]

7. cot^2 A(sec^2 A− 1 )= 1
   [coth^2 θ( 1 −sech^2 θ)=1]