Question #32016

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Answer 1 · 2015-08-15T16:21:00

Refer below

#cos((3pi)/2 + x)#
#= cos(-pi/2 + x)# (because #cos x = cos (x+2pi)#)
#= cos (pi/2 - x)# (because #cos (-x) = cos x#)
#= sin x#
#= 0.3#

Answer 2 · 2015-08-15T17:16:09

The answer is #cos((3pi)/2+x) = 0.3#. Here is a different path than Joel Kindiak's to the same answer.

Use the cosine of a sum formula:

#cos((3pi)/2+x) = cos((3pi)/2)cos(x)-sin((3pi)/2)sin(x)#

# = (-1)cos(x) - (-1)(0.3)#

# = 0.3#