Question : If 0.5i+0.8j+ck is a unit vector, then the value of c is
a) √0.11
b) √0.22
c) √0.33
d) √0.89
Doubt by Avani
Solution :
Let A=0.5i+0.8j+ck
A is a unit vector (Given)
The magnitude of a unit vector is 1 i.e A=1
A=√[(0.5)²+(0.8)²+(c)²]
Squaring both sides
A² = 0.25+0.64+c²
(1)²=0.89+c²
1-0.89=c²
√0.11=c
c=√0.11
Hence, a) √0.11 would be the correct option.
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