The answer to whether tan(-x)=cos(x) is False

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prove tan(-x)=cos(x)

Solution

prove

tan (- x) = cos (x)

False

Solution steps

tan (- x) = cos (x)

Show that the two sides are not equal

For

tan (- x) = cos (x)

plug in

x = 0

tan (- 0) = 0

tan (- 0)

Simplify

= tan (0)

Use the following trivial identity:

tan (0) = 0

tan (0)

tan (x)

periodicity table with

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} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

= 0

= 0

cos (0) = 1

cos (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

= 1

The two sides are not equal

\Rightarrow False

\frac{1}{cos ( x )} - cos (x) = tan (x) sin (x)

cos (4 5^{\circ} - x) = cos (x - 4 5^{\circ})

\frac{1 - csc ^{2} ( A )}{csc ^{2} ( A )} = - cos^{2} (A)

csc (x) (sec (x)) = tan (x)

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