Use the information below to answer question 15 to 20 Given that x=rsincos,y=rsinsin,z=rcos,r2=x2+y2+ z2 and u(x,y,z) 15. Which of the following statement is equal to zuz A. yuyu+rur B. uxyuyxux C. xux+uyuy D. uyuyxurx Find ru A. cossinxu+rcossinu+coszu B. coszu+cossinxu+cossinu C. rcossinucossinxu+coszu D. sinzu+rcosxu+sinrcosu 17. Which of the following statement is equal to zu A. rsin2coscossinu+sincos2cosxusin1u B. rsin2cossincosu+sincoscosxursin1u C. rsin2cossincosu+sincoscosxursin1u D. rsin2coscossinu+sincoscosxursin1u Simplify r1u A. r31[r(cosr2ru)+r2122u] B. r31[r(r2ru)+sin2122u+sin1(sinu)] C. r31[r(r2ru)+rsin2122u+sin1(sinu)] D. r31[r(r1ru)+sin122u+sin1(sinu)] Find ru A. sinsinyu+coscosxu+coszu B. coscosyu+sincosxu+coszu C. coszu+sincosxu+sinsinyu D. sincosxu+coszu+sinsinyu Find X(u)+u A. r2122u+z22u+r22u+r1ru B. r1ru+sinr2u+z22u+r2122u+r22u C. z22u+r2122u+r2r22u+ru D. rcosru+22u+sin1z22u+rr22u