(2cos^2a - 1)/(sin^2(a + pi/4)tg(a + pi/4)

​​$A=\frac{2{\cos }^{2}a-1}{{\sin }^2(a+{\displaystyle \frac{\mathrm{\pi }}{4}}).tg(a+\frac{\mathrm{\pi }}{4})}$
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