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Solve trig equation in a given internval with stretch and worked solutions
", "licence": "Creative Commons Attribution-NonCommercial 4.0 International"}, "statement": "Trig Equation with a stretch
", "advice": "\\begin{align}
cos(2x) & =\\var{a} \\\\\\\\
2x & = cos^{-1}\\var{a}=\\var{x1x2_5} \\text{ or } 2\\pi-\\var{x1x2_5} \\\\\\\\
\\text{(To find a second angle you could also use $-\\var{x1x2_5}$ and then add $2\\pi$)} \\\\\\\\
2x & = \\var{x1x2_5} \\text{ or } \\var{x2x2_5} \\\\\\\\
\\text{You can now add $2\\pi$ to both of these angles to find extra angles} \\\\\\\\
2x & = \\var{x1x2_5} \\text{ or } \\var{x2x2_5} \\text{ or } (\\var{x1x2_5}+2\\pi) \\text{ or } (\\var{x2x2_5}+2\\pi) \\\\\\\\
2x & = \\var{x1x2_5} \\text{ or } \\var{x2x2_5} \\text{ or } \\var{x3x2_5} \\text{ or } \\var{x4x2_5} \\\\\\\\
x &= \\var{x1_3}^c \\text{ or }\\var{x2_3}^c \\text{ or }\\var{x3_3}^c \\text{ or }\\var{x4_3}^c \\text{ to 3 sig fig}
\\end{align}
Solve $cos(2x)=\\var{a}$ between $0 \\leq x \\leq 2\\pi$
\n\nEnter your answers below giving the angles in ascending order and to 3 significant figures.
\n\n$x=$ [[3]]$^c$ or [[0]]$^c$ or [[1]]$^c$ or [[2]]$^c$
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