The Total solution for NCERT class 6-12
Show that 1 + i10 + i20 + i30 isa real number?
Given:
1 + i10 +i20 + i30 = 1 + i(8 + 2) + i20 +i(28 + 2)
= 1 + (i4)2 ×i2 + (i4)5 + (i4)7 ×i2
= 1 – 1 + 1 – 1[since, i4 = 1, i2 = – 1]
= 0
Hence , 1 + i10 +i20 + i30 is a real number.