cos(π/12)^4+sin(π/12)^4
=(cos²(12π)+sin²(12π))²-2sin²(12π)cos²(12π)
=1-(√2sin(12π)cos(12π))²
=1-(2√2sin6π)²
∵sin(6π)=21
∴原式=1-(2√2•21)²
=1-81
=87
cos(π/12)^4+sin(π/12)^4=
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