25-x²>16
-x²>-9
x<+-3
x∈(-3;3)
Решение
ctg²a + 1 = 1/sin²a
<span>ctg²a = 1/sin²a - 1
</span>ctg²a = 1/(8/√65)²<span> - 1
</span>ctg²a = (√65/8)²<span> - 1
</span>ctg²a = 65/64<span> - 1
</span>ctg²a = (65 - 64)/64
<span>ctg²a = 1/64
</span>ctga = √(1/64)
1) ctga = - 1/8
<span>2) ctga = 1/8</span>
4xy × 3y⁷ = 12xy⁸
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