<span>2tgx + 2ctgx = 5</span>
<span>2tgx + 2/tgx - 5 = 0</span>
<span>2tg²x - 5tgx + 2 = 0</span>
<span>замена: tgx = a</span>
<span>2a² - 5a + 2 = 0</span>
<span>a₁ = 2, a₂ = 1/2</span>
<span>обратная замена:</span>
<span>tgx = 2</span>
<span>x = arctg2 + πn, n∈Z</span>
<span>tgx = 1/2</span>
<span>x = arctg(1/2) + πn, n∈Z</span>