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Created a notebook describing a new, easy memorization technique I le…
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…arned for remembering the values of sin and cos for standard angles on the unit circle. Also added a Trigonometry directory.
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Tom Malone committed Oct 31, 2015
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{
"cells": [
{
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"source": [
"# Memorizing the Unit Circle\n",
"\n",
"<p class='lead'>This is a great, very easy technique for remembering the values of the sine and cosine of any angle on the unit circle.</p>\n",
"\n",
"<p class='lead'>All you have to remember is: $0, 1, 2, 3, \\text{ and } 4$ and $\\frac{\\sqrt{x}}{2}$.</p>\n",
"\n",
"---"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Sine \n",
"\n",
"Beginning in __Quadrant I__ with angle $\\angle \\theta = 0$, _all_ you have to do is remember to replace $x$ in $\\frac{\\sqrt{x}}{2}$ with $0, 1, 2, 3, \\text{ or } 4$:\n",
" \n",
"<table width='100%' align='left'>\n",
"<tr>\n",
" <th>Number</th>\n",
" <th>$\\text{Value of } \\theta$</th>\n",
" <th>$\\sin(\\theta)$</th>\n",
" <th>Actual Value of $\\sin$</th>\n",
"</tr>\n",
"<tr>\n",
" <td>0:</td>\n",
" <td>$0$</td>\n",
" <td>$\\sin(0) = \\frac{\\sqrt{\\color{red}0}}{2}$</td>\n",
" <td>$0$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>1:</td>\n",
" <td>$\\frac{\\pi}{6}$ / $30\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{6}) = \\frac{\\sqrt{\\color{red}1}}{2} = \\frac{1}{2}$</td>\n",
" <td>$\\frac{1}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>2:</td>\n",
" <td>$\\frac{\\pi}{4}$ / $45\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{4}) = \\frac{\\sqrt{\\color{red}2}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{2}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>3:</td>\n",
" <td>$\\frac{\\pi}{3}$ / $60\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{3}) = \\frac{\\sqrt{\\color{red}3}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{3}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>4:</td>\n",
" <td>$\\frac{\\pi}{2}$ / $90\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{2}) = \\frac{\\sqrt{\\color{red}4}}{2} = \\frac{2}{2} = 1$</td>\n",
" <td>$1$</td>\n",
"</tr>\n",
"</table>\n",
"\n",
"<br/><br/>\n",
"For __Quadrant II__, the values count back down from $\\frac{\\sqrt{4}}{2}$ to $\\frac{\\sqrt{0}}{2}:$\n",
"\n",
"<table width='100%' align='left'>\n",
"<tr>\n",
" <th>Number</th>\n",
" <th>$\\text{Value of } \\theta$</th>\n",
" <th>$\\sin(\\theta)$</th>\n",
" <th>Actual Value of $\\sin$</th>\n",
"</tr>\n",
"<tr>\n",
" <td>4:</td>\n",
" <td>$\\frac{\\pi}{2}$ / $90\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{2}) = \\frac{\\sqrt{\\color{red}4}}{2} = \\frac{2}{2} = 1$</td>\n",
" <td>$1$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>3:</td>\n",
" <td>$\\frac{2\\pi}{3} (= \\frac{4\\pi}{6})$ / $120\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{3}) = \\frac{\\sqrt{\\color{red}3}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{3}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>2:</td>\n",
" <td>$\\frac{\\pi}{4}$ / $45\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{4}) = \\frac{\\sqrt{\\color{red}2}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{2}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>1:</td>\n",
" <td>$\\frac{\\pi}{6}$ / $30\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{6}) = \\frac{\\sqrt{\\color{red}1}}{2} = \\frac{1}{2}$</td>\n",
" <td>$\\frac{1}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>0:</td>\n",
" <td>$\\frac{2\\pi}{2} (= \\pi)$ / $180\\circ$</td>\n",
" <td>$\\sin(\\pi) = \\frac{\\sqrt{\\color{red}0}}{2} = 0$</td>\n",
" <td>$1$</td>\n",
"</tr>\n",
"</table>"
]
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137 changes: 137 additions & 0 deletions Trigonometry/Easy_Way_to_Memorize_Unit_Circle.ipynb
Original file line number Diff line number Diff line change
@@ -0,0 +1,137 @@
{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Memorizing the Unit Circle\n",
"\n",
"<p class='lead'>This is a great, very easy technique for remembering the values of the sine and cosine of any angle on the unit circle.</p>\n",
"\n",
"<p class='lead'>All you have to remember is: $0, 1, 2, 3, \\text{ and } 4$ and $\\frac{\\sqrt{x}}{2}$.</p>\n",
"\n",
"---"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Sine \n",
"\n",
"Beginning in __Quadrant I__ with angle $\\angle \\theta = 0$, _all_ you have to do is remember to replace $x$ in $\\frac{\\sqrt{x}}{2}$ with $0, 1, 2, 3, \\text{ or } 4$:\n",
" \n",
"<table width='100%' align='left'>\n",
"<tr>\n",
" <th>Number</th>\n",
" <th>$\\text{Value of } \\theta$</th>\n",
" <th>$\\sin(\\theta)$</th>\n",
" <th>Actual Value of $\\sin$</th>\n",
"</tr>\n",
"<tr>\n",
" <td>0:</td>\n",
" <td>$0$</td>\n",
" <td>$\\sin(0) = \\frac{\\sqrt{\\color{red}0}}{2}$</td>\n",
" <td>$0$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>1:</td>\n",
" <td>$\\frac{\\pi}{6}$ / $30\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{6}) = \\frac{\\sqrt{\\color{red}1}}{2} = \\frac{1}{2}$</td>\n",
" <td>$\\frac{1}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>2:</td>\n",
" <td>$\\frac{\\pi}{4}$ / $45\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{4}) = \\frac{\\sqrt{\\color{red}2}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{2}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>3:</td>\n",
" <td>$\\frac{\\pi}{3}$ / $60\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{3}) = \\frac{\\sqrt{\\color{red}3}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{3}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>4:</td>\n",
" <td>$\\frac{\\pi}{2}$ / $90\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{2}) = \\frac{\\sqrt{\\color{red}4}}{2} = \\frac{2}{2} = 1$</td>\n",
" <td>$1$</td>\n",
"</tr>\n",
"</table>\n",
"\n",
"<br/><br/>\n",
"For __Quadrant II__, the values count back down from $\\frac{\\sqrt{4}}{2}$ to $\\frac{\\sqrt{0}}{2}:$\n",
"\n",
"<table width='100%' align='left'>\n",
"<tr>\n",
" <th>Number</th>\n",
" <th>$\\text{Value of } \\theta$</th>\n",
" <th>$\\sin(\\theta)$</th>\n",
" <th>Actual Value of $\\sin$</th>\n",
"</tr>\n",
"<tr>\n",
" <td>4:</td>\n",
" <td>$\\frac{\\pi}{2}$ / $90\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{2}) = \\frac{\\sqrt{\\color{red}4}}{2} = \\frac{2}{2} = 1$</td>\n",
" <td>$1$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>3:</td>\n",
" <td>$\\frac{2\\pi}{3} (= \\frac{4\\pi}{6})$ / $120\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{3}) = \\frac{\\sqrt{\\color{red}3}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{3}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>2:</td>\n",
" <td>$\\frac{\\pi}{4}$ / $45\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{4}) = \\frac{\\sqrt{\\color{red}2}}{2}$</td>\n",
" <td>$\\frac{\\sqrt{2}}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>1:</td>\n",
" <td>$\\frac{\\pi}{6}$ / $30\\circ$</td>\n",
" <td>$\\sin(\\frac{\\pi}{6}) = \\frac{\\sqrt{\\color{red}1}}{2} = \\frac{1}{2}$</td>\n",
" <td>$\\frac{1}{2}$</td>\n",
"</tr>\n",
"<tr>\n",
" <td>0:</td>\n",
" <td>$\\frac{2\\pi}{2} (= \\pi)$ / $180\\circ$</td>\n",
" <td>$\\sin(\\pi) = \\frac{\\sqrt{\\color{red}0}}{2} = 0$</td>\n",
" <td>$1$</td>\n",
"</tr>\n",
"</table>"
]
},
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