$\tg^2{x}+1$
$\ctg^2{x}+1$
$2\sin{x}\cos{x}$
Три формулы $\cos^2{x}-\sin^2{x}$
$3\sin{x}-4\sin^3{x}$
$4\cos^3{x}-3\cos{x}$
$\dfrac{2\tg{x}}{1-\tg^2{x}}$
$\sin{x}\cos{y}+\cos{x}\sin{y}$
$\sin{x}\cos{y}-\cos{x}\sin{y}$
$\cos{x}\cos{y}-\sin{x}\sin{y}$
$\cos{x}\cos{y}+\sin{x}\sin{y}$
$\dfrac{\tg{x}+\tg{y}}{1-\tg{x}\tg{y}}$
$\dfrac{\tg{x}-\tg{y}}{1+\tg{x}\tg{y}}$
$\dfrac{1-\cos{2x}}{2}$
$\dfrac{1+\cos{2x}}{2}$
$\dfrac{2\tg{\dfrac{x}{2}}}{ 1+\tg^2{\dfrac{x}{2}}}$
$\dfrac{1-\tg^2{\dfrac{x}{2}}}{1+\tg^2{\dfrac{x}{2}}}$
$2\cos{\dfrac{x+y}{2}}\cos{\dfrac{x-y}{2}}$
$-2\sin{\dfrac{x+y}{2}}\sin{\dfrac{x-y}{2}}$
$2\sin{\dfrac{x+y}{2}}\cos{\dfrac{x-y}{2}}$
$2\sin{\dfrac{x-y}{2}}\cos{\dfrac{x+y}{2}}$
$\dfrac{1}{2}(\cos{(x-y)}+\cos{(x+y)})$
$\dfrac{1}{2}(\cos{(x-y)}-\cos{(x+y)})$
$\dfrac{1}{2}(\sin{(x-y)}+\sin{(x+y)})$