How do you evaluate e^( ( pi)/4 i) - e^( ( 35 pi)/4 i)eπ4ie35π4i using trigonometric functions?

1 Answer
Mar 28, 2016

e^((pi)/4i)-e^((35pi)/4i)=sqrt2eπ4ie35π4i=2

Explanation:

As e^(itheta)=costheta+isinthetaeiθ=cosθ+isinθ, we have

e^((pi)/4i)=cos((pi)/4)+isin((pi)/4)=1/sqrt2+i1/sqrt2eπ4i=cos(π4)+isin(π4)=12+i12

e^((35pi)/4i)=cos((35pi)/4)+isin((35pi)/4)e35π4i=cos(35π4)+isin(35π4)

= cos(8pi+(3pi)/4)+isin(8pi+(3pi)/4)cos(8π+3π4)+isin(8π+3π4)

= cos((3pi)/4)+isin((3pi)/4)cos(3π4)+isin(3π4)

= cos(pi-(pi)/4)+isin(pi-pi/4)cos(ππ4)+isin(ππ4)

= -cos((pi)/4)+isin(pi/4)cos(π4)+isin(π4)

= -1/sqrt2+i1/sqrt212+i12

Hence e^((pi)/4i)-e^((35pi)/4i)=(1/sqrt2+i1/sqrt2)-(-1/sqrt2+i1/sqrt2)eπ4ie35π4i=(12+i12)(12+i12)

= (1/sqrt2+1/sqrt2)+i(1/sqrt2-1/sqrt2)(12+12)+i(1212)

= 2/sqrt2+0=sqrt222+0=2