write the following complex number in polar form. Express all angles in degrees rounded to the nearest tenth.

r  =  sqrt ( 2^2 + (√21)^2 )  =  sqrt ( 4 + 21)  = sqrt (25) = 5

 θ = arctan ( √21 / 2) ≈  66.4°  

5cos(66.4°) + 5i sin (66.4°)   =  5 [ cos (66.4°  + i sin (66.4° ) ]