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5 votes
3sina-4sin4a/sin5a
if a=-45 degree

User Roshanna
by
8.0k points

1 Answer

3 votes

Given:

The given expression is:


(3\sin a-4\sin 4a)/(\sin 5a)

To find:

The value of the given expression at
a=-45.

Solution:

We have,


(3\sin a-4\sin 4a)/(\sin 5a)

Substituting
a=-45, we get


(3\sin (-45)-4\sin [4(-45)])/(\sin [5(-45)])


=(-3\sin (45)+4\sin (180))/(-\sin (225))


=(-3\sin (45)+4\sin (180))/(-\sin (180+45))


=(-3\sin (45)+4\sin (180))/(\sin (45))

On substituting
\sin (180), we get,


=(-3\sin (45)+4(0))/(\sin (45))


=(-3\sin (45)+0)/(\sin (45))


=(-3\sin (45))/(\sin (45))


=-3

Therefore, the value of the given expression at
a=-45 is
-3.

User Skwal
by
9.0k points

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