Posted by Angela on Wednesday, October 7, 2009 at 10:31pm.
I am trying to find the inverse of matrix A but I don't know how to do it with sin and cos. Please help.
A=6e3tsin(6t) −6e4tcos(6t)
−5e3tcos(6t) −5e4tsin(6t)
then A−1=

linear algebra  MathMate, Wednesday, October 7, 2009 at 10:52pm
The inverse of a 2x2 can be done as follows:
For matrix, A=
a b
c d
The inverse A^{1}=
d b
c a / (adbc)
For example:
If A=
4 5
6 7
A^{1} =
7 5
6 4 / (2830)
=
3.5 2.5
3 2
Check:
4 5 3.5 2.5
6 7 3 2
=
1 0
0 1