1.

The projection of the vector hati+3hatj+7hatk on the vector 7hati-hatj+8hatk is

Answer»

`(60)/(sqrt(122))`
`(30)/(sqrt(144))`
`(60)/(sqrt(114))`
`(60)/(sqrt(111))`

Solution :Let ` a = hati + 3 hatj+ 7 HATK` and ` 7 hati - hatj +8hatk,`thenprojectionof aonb is givenby
` (a.b) /(|b|)=[((hati +3hatj +7 hatk).(7 hati -hatj+8hatk))/(sqrt(7)^(2)+(-1)^(2)+8^(2))]`
`=[(1xx7+3xx(-1)+7xx8)/((sqrt(49)+1+64))]=(7-3+56)/(sqrt(114))=(60)/(sqrt(114))`


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