cos(a)=(sqrt(5))/5

解

cos (a) = \frac{5}{5}

a = 1.10714 \dots + 2 πn, a = 2 π - 1.10714 \dots + 2 πn

度

a = 63.43494 \dots^{\circ} + 36 0^{\circ} n, a = 296.56505 \dots^{\circ} + 36 0^{\circ} n

解答ステップ

cos (a) = \frac{5}{5}

三角関数の逆数プロパティを適用する

cos (a) = \frac{5}{5}

以下の一般解

cos (a) = \frac{5}{5}

cos (x) = a \Rightarrow x = arccos (a) + 2 πn, x = 2 π - arccos (a) + 2 πn

a = arccos (\frac{5}{5}) + 2 πn, a = 2 π - arccos (\frac{5}{5}) + 2 πn

a = arccos (\frac{5}{5}) + 2 πn, a = 2 π - arccos (\frac{5}{5}) + 2 πn

10進法形式で解を証明する

a = 1.10714 \dots + 2 πn, a = 2 π - 1.10714 \dots + 2 πn