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If √2 cos x = cosy + cos3y and √2 sinx = siny − sin3y then determine the value of  sin(x − y)

5 years ago


Answers : (1)


Dear Nirabhra


=1/√2 [(siny-sin3y)*cosy - (cosy + cos3y)*siny]

=1/√2 [siny(1-sin2y)*cosy - (cosy + cos3y)*siny]

=1/√2 [siny*cos2y*cosy - (cosy + cos3y)*siny]

=1/√2 [siny*cos3y - (cosy + cos3y)*siny]

take siny common

=1/√2 * siny [cos3y - cosy - cos3y]

= - siny*cosy/√2

= -sin2y/2√2

All the best.




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5 years ago

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