cot (A/2) = √ { (1+cosA)/ (1-cosA)} ? 两角和公式 sin (A+B) = sinAcosB+cosAsinB sin (A-B) = sinAcosB-cosAsinB cos (A+B) = cosAcosB-sinAsinB cos (A-B) = cosAcosB+sinAsinB tan (A+B) = (tanA+tanB)/ (1-tanAtanB) tan (A-B) = (tanA-tanB)/ (1+tanAtanB)…

Take the inverse cosine of both sides of the equation to extract x x from inside the cosine. Simplify the right side. Tap for more steps... The cosine function is positive in the first and fourth …

\sec x = \frac {1} {\cos {x}} \csc {x} = \frac {1} {\sin {x}} \cot {x} = \frac {1} {\tan {x}} \sin^ {2}x + \cos^ {2}x = 1. 1 + \tan^ {2} x = \sec^ {2}x. 1 + \cot^ {2}x = \csc^ {2}x. \tan {x} = \frac {\sin {x}} {\cos {x}} = \frac {\sec {x}} {\csc {x}} \cot {x} = \frac {\cos {x}} {\sin {x}} = \frac {\csc {x}} {\sec {x}}

In basic trigonometry computes sine, cosine, tangent, and their reciprocal. Calculates arcsin, arccos, and arctan values inside inverse trigonometric equations. Trigonometric identities …

k = ...,-2,-1,0,1,2,... Cosine calculator online. cos (x) calculator.

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在 数学 中， 三角恒等式 是对出现的所有值都为 實变量，涉及到 三角函数 的等式。 这些 恒等式 在表达式中有些三角函数需要简化的时候是很有用的。 一个重要应用是非三角函数的 积分：一个常用技巧是首先使用 使用三角函数的代换规则，则通过三角恒等式可简化结果的积分。 为了避免由于 的不同意思所带来的混淆，我們經常用下列兩個表格來表示 三角函数 的 倒数 和 反函数。 另外在表示 余割函数 時，' '有时會寫成比較长的' '。 不同的角度度量适合于不同的情况。 本表 …

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You can use a reduction formula. See explanation. Explanation: \displaystyle {\cos { {120}}}= {\cos { {\left ( {180}- {60}\right)}}}=- {\cos { {60}}}=-\frac { {1}} { {2}}