If adenine is 31% in DNA, calculate the percentage of cytosine. Explain briefly.
Adenine pairs with thymine (31% each), totaling 62\%. Cytosine and guanine share the remaining 38%. Therefore, cytosine is 19%, following Chargaff’s rule, where purines (adenine, guanine) always pair with pyrimidines (thymine, cytosine).
If vector \( \mathbf{a} = 3 \hat{i} + 2 \hat{j} - \hat{k} \) \text{ and } \( \mathbf{b} = \hat{i} - \hat{j} + \hat{k} \), then which of the following is correct?