2007-02-24 04:43:45 · 5 answers · asked by 47 2 in Science & Mathematics ➔ Mathematics
The period of cos(x) is 360 degrees. If you shift the curve by half of its period (180 degrees), you've essentially reflected the curve about the x-axis.
2007-02-24 04:51:03 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Use the formula for the cos of the difference of two angles:
cos(180-Î) = cos180cosÎ +sin180sinÎ
Since cos 180 = -1 and sin 180 = 0, we get:
cos(180-Î) = -cosÎ
2007-02-24 12:54:15 · answer #2 · answered by ironduke8159 7 · 0⤊ 0⤋
Think about a unit circle. In a unit circle, cosÎ = x. Whenever you turn it by 180 degrees, x keeps the same magnititude but changes the sign.
2007-02-24 12:54:03 · answer #3 · answered by sahsjing 7 · 0⤊ 0⤋
The formula for cos(a-b) is cosacosb+sinasinb.
Plug in 180 for a and theta for b. Use the unit circle. Cosa is -1 and sina is 0. Solve.
2007-02-24 12:49:09 · answer #4 · answered by Blarepen 2 · 0⤊ 0⤋
because
cos 180 = -1
2007-02-24 12:50:32 · answer #5 · answered by Anonymous · 0⤊ 0⤋