Question

Find the rectangular coordinates of the point that has polar coordinates , 4, −3π/4

Answer 1

hello : 
 x= r cosθ
 y= r sinθ
r = 4   and  θ = −3π/4
cos(  −3π/4 )  = cos(  3π/4 ) = cos ( π - π/4) = - cos (π/4)= - √2/2
sin(  −3π/4 )  =  -  sin(  3π/4 ) = - sin ( π - π/4) = -sin (π/4)= - √2/2
x = - 2 √2
 y = - 2 √2