Is sin^2(x)-cos^2(x)=1 ?

The answer to whether sin^2(x)-cos^2(x)=1 is False

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prove sin^2(x)-cos^2(x)=1

prove

sin^{2} (x) - cos^{2} (x) = 1

False

Solution steps

sin^{2} (x) - cos^{2} (x) = 1

Show that the two sides are not equal

For

sin^{2} (x) - cos^{2} (x) = 1

plug in

x = 0

sin^{2} (0) - cos^{2} (0) = - 1

sin^{2} (0) - cos^{2} (0)

Use the following trivial identity:

sin (0) = 0

sin (0)

sin (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} sin (x) 0 \frac{1}{2} \frac{2}{2} \frac{3}{2} 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} sin (x) 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2}

= 0

Use the following trivial identity:

cos (0) = 1

cos (0)

cos (x)

periodicity table with

2 πn

cycle:

x 0 \frac{π}{6} \frac{π}{4} \frac{π}{3} \frac{π}{2} \frac{2 π}{3} \frac{3 π}{4} \frac{5 π}{6} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x π \frac{7 π}{6} \frac{5 π}{4} \frac{4 π}{3} \frac{3 π}{2} \frac{5 π}{3} \frac{7 π}{4} \frac{11 π}{6} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

= 1

= 0^{2} - 1^{2}

Simplify

= - 1

The two sides are not equal

\Rightarrow False

cot^{4} (x) + 2 cot^{2} (x) = csc^{4} (x) - 1

\frac{sin ( 2 x )}{2} = \frac{1}{2} sin (2 x)

cot (3) = \frac{cos ( 3 )}{sin ( 3 )}

\frac{2 - 2 sin ^{2} ( x )}{sin ( x )} = cot (x)

cos (2 θ) - cos (θ) + 1 = 0