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\(练练手。记\theta=2a\)
\(可以有:\frac{\sin(a)}{\cos(a)}=\frac{\sin(2a)}{1+\cos(2a)}=\frac{1-\cos(2a)}{\sin(2a)}\)
\(\frac{\sin(a)}{\cos(a)}=\frac{\sin(2a)}{1+\cos(2a)},可以有:\frac{\sin(a)}{\cos(a)}=\frac{2\sin(a)\cos(a)}{2\cos^2(a)}\)
\(\frac{\sin(a)}{\cos(a)}=\frac{1-\cos(2a)}{\sin(2a)},可以有:\frac{\sin(a)}{\cos(a)}=\frac{2\sin^2(a)}{2\sin(a)\cos(a)}\)
\(\frac{\sin(2a)}{1+\cos(2a)}=\frac{1-\cos(2a)}{\sin(2a)},可以有:\frac{2\sin(a)\cos(a)}{2\cos^2(a)}=\frac{2\sin^2(a)}{2\sin(a)\cos(a)}\) |
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