三角函数公式整理
Posted henry-1202
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诱导公式
奇变偶不变，符号看象限
[
egin{aligned}
&cos {left(pi + alpha
ight)} =-cos alpha&sin {left( pi + alpha
ight) } = -sin alpha& an {left( pi + alpha
ight)} = an alpha
end{aligned}
]
[ egin{aligned} &cos {left(-alpha ight)} =cos alpha&sin {left(-alpha ight) } = -sin alpha& an {left(-alpha ight)} = - an alpha end{aligned} ]
[ egin{aligned} &cos {left(pi - alpha ight)} =-cos alpha&sin {left( pi - alpha ight) } = sin alpha& an {left( pi - alpha ight)} = - an alpha end{aligned} ]
[ egin{aligned} &cos {left(frac pi 2 - alpha ight)} =sin alpha&sin {left( frac pi 2 - alpha ight) } = cos alpha\end{aligned} ]
[ egin{aligned} &cos {left(frac pi 2 + alpha ight)} =-sin alpha&sin {left( frac pi 2 + alpha ight) } = cos alpha\end{aligned} ]
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