sin Cosine calculator ► Sine calculation Calculation with sinangle degrad Expression Result Inverse sine calculator sin-1 Degrees First result Second result Radians First result Second result k = ...,-2,-1,0,1,2,... Arcsin calculator ► Sine table xdeg xrad sinx -90° -π/2 -1 -60° -π/3 -√3/2 -45° -π/4 -√2/2 -30° -π/6 -1/2 0° 0 0 30° π/6 1/2 45° π/4 √2/2 60° π/3 √3/2 90° π/2 1 See also Sine function Cosine calculator Tangent calculator Arcsin calculator Arccos calculator Arctan calculator Trigonometry calculator Degrees to radians conversion Radians to degrees conversion Degrees to degrees,minutes,seconds Degrees,minutes, seconds to degrees Write how to improve this page
Weknow that cos ( A B) = cos A cos B + sin A sin B Hence A = (n + 1)x ,B = (n + 2)x Hence sin ( + 1) sin ( + 2) +cos ( + 1) cos ( + 2) = cos [ (n + 1)x (n + 2)x ] = cos [ nx + x nx 2x ] = cos [ nx nx x 2 x ] = cos (0 x ) = cos ( x) = cos x = R.H.S. Hence , L.H.S. = R.H.S. Hence proved
If $n$ is even, then $$1= \cos^{n}x-\sin^{n}x \leq 1-0=1$$ with equality if and only if $\cos^{n}x=1, \sin^nx=0$. If $n$ is odd, $$1= \cos^{n}x-\sin^{n}x \,,$$ implies $\cosx \geq 0$ and $\sinx <0$. Let $\cosx=y, \sinx=-z$, with $y,z \geq 0$. $$y^n+z^n=1$$ $$y^2+z^2=1$$ Case 1 $n=1$ Then , since $0 \leq y,z \leq 1$ we have $$1 =y+z \geq y^2+z^2 =1$$ with equality if and only if $y=y^2, z=z^2$. Case 2 $n \geq 3$ Then , since $0 \leq y,z \leq 1$ we have $$1 =y^2+z^2 \geq y^n+z^n =1$$ with equality if and only if $y^2=y^n, z^2=z^n$.