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আপনার প্রশ্নটিঃ- cos² π/8 + cos² (3π/8) + cos² (5π/8)+ cos²(7π/8) = cos²π/8 + cos²{(π/2)-(π/8)} + cos²{(π/2)+(π/8)}+ cos²{π-(π/8)} = cos²π/8 + sin²π/8 + sin²π/8+cos²π/8 =2(cos²π/8+sin²π/8) = 2×1 =2.
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