cos(x)=(6.5)/(8.4)

解

cos (x) = \frac{6.5}{8.4}

x = 0.68596 \dots + 2 πn, x = 2 π - 0.68596 \dots + 2 πn

度

x = 39.30277 \dots^{\circ} + 36 0^{\circ} n, x = 320.69722 \dots^{\circ} + 36 0^{\circ} n

解答ステップ

cos (x) = \frac{6.5}{8.4}

三角関数の逆数プロパティを適用する

cos (x) = \frac{6.5}{8.4}

以下の一般解

cos (x) = \frac{6.5}{8.4}

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

x = arccos (\frac{6.5}{8.4}) + 2 πn, x = 2 π - arccos (\frac{6.5}{8.4}) + 2 πn

x = arccos (\frac{6.5}{8.4}) + 2 πn, x = 2 π - arccos (\frac{6.5}{8.4}) + 2 πn

10進法形式で解を証明する

x = 0.68596 \dots + 2 πn, x = 2 π - 0.68596 \dots + 2 πn