MathematicsEasy202×since 2002Q5694Let a, b and c be distinct positive numbers. If the vectors ai^+aj^+ck^,i^+k^a\widehat i + a\widehat j + c\widehat k,\widehat i+\widehat kai+aj+ck,i+k and ci^+cj^+bk^c\widehat i + c\widehat j + b\widehat kci+cj+bk are co-planar, then c is equal to :A21a+1b{2 \over {{1 \over a} + {1 \over b}}}a1+b12Ba+b2{{a + b} \over 2}2a+bC1a+1b{1 \over a} + {1 \over b}a1+b1Dab\sqrt {ab}abCheck answerSkip