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Evaluate : \(\begin{vmatrix}a\,+ & c\,+ \\[0.3em]-c\,+ & a\,- \\[0.3em]\end{vmatrix}\) |
Answer» (a + ib)(a - ib) - (c + id)(- c + id) = [a2 - i2b2] - [i2d2 - c2] = (a2 + b2) - (- d2 - c2) [∵ i2 = -1] = a2 +b2 + d2 + c2 = a2 + b2 + c2 + d2 |
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