Is cot(a)=tan(pi/2-a) ?

The answer to whether cot(a)=tan(pi/2-a) is True

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Popular Trigonometry >

prove cot(a)=tan(pi/2-a)

Solution

prove

cot (a) = tan (\frac{π}{2} - a)

Solution

True

Solution steps

cot (a) = tan (\frac{π}{2} - a)

Manipulating right side

tan (\frac{π}{2} - a)

Rewrite using trig identities

tan (\frac{π}{2} - a)

Use the basic trigonometric identity:

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

= \frac{sin ( \frac{π}{2} - a )}{cos ( \frac{π}{2} - a )}

Use the Angle Difference identity:

sin (s - t) = sin (s) cos (t) - cos (s) sin (t)

= \frac{sin ( \frac{π}{2} ) cos ( a ) - cos ( \frac{π}{2} ) sin ( a )}{cos ( \frac{π}{2} - a )}

Use the Angle Difference identity:

cos (s - t) = cos (s) cos (t) + sin (s) sin (t)

= \frac{sin ( \frac{π}{2} ) cos ( a ) - cos ( \frac{π}{2} ) sin ( a )}{cos ( \frac{π}{2} ) cos ( a ) + sin ( \frac{π}{2} ) sin ( a )}

Simplify

\frac{sin ( \frac{π}{2} ) cos ( a ) - cos ( \frac{π}{2} ) sin ( a )}{cos ( \frac{π}{2} ) cos ( a ) + sin ( \frac{π}{2} ) sin ( a )} : \frac{cos ( a )}{sin ( a )}

\frac{sin ( \frac{π}{2} ) cos ( a ) - cos ( \frac{π}{2} ) sin ( a )}{cos ( \frac{π}{2} ) cos ( a ) + sin ( \frac{π}{2} ) sin ( a )}

sin (\frac{π}{2}) cos (a) - cos (\frac{π}{2}) sin (a) = cos (a)

sin (\frac{π}{2}) cos (a) - cos (\frac{π}{2}) sin (a)

sin (\frac{π}{2}) cos (a) = cos (a)

sin (\frac{π}{2}) cos (a)

Simplify

sin (\frac{π}{2}) : 1

sin (\frac{π}{2})

Use the following trivial identity:

sin (\frac{π}{2}) = 1

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}

= 1

= 1 \cdot cos (a)

Multiply:

1 \cdot cos (a) = cos (a)

= cos (a)

cos (\frac{π}{2}) sin (a) = 0

cos (\frac{π}{2}) sin (a)

Simplify

cos (\frac{π}{2}) : 0

cos (\frac{π}{2})

Use the following trivial identity:

cos (\frac{π}{2}) = 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}

= 0

= 0 \cdot sin (a)

Apply rule

0 \cdot a = 0

= 0

= cos (a) - 0

cos (a) - 0 = cos (a)

= cos (a)

= \frac{cos ( a )}{cos ( \frac{π}{2} ) cos ( a ) + sin ( \frac{π}{2} ) sin ( a )}

cos (\frac{π}{2}) cos (a) + sin (\frac{π}{2}) sin (a) = sin (a)

cos (\frac{π}{2}) cos (a) + sin (\frac{π}{2}) sin (a)

cos (\frac{π}{2}) cos (a) = 0

cos (\frac{π}{2}) cos (a)

Simplify

cos (\frac{π}{2}) : 0

cos (\frac{π}{2})

Use the following trivial identity:

cos (\frac{π}{2}) = 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}

= 0

= 0 \cdot cos (a)

Apply rule

0 \cdot a = 0

= 0

sin (\frac{π}{2}) sin (a) = sin (a)

sin (\frac{π}{2}) sin (a)

Simplify

sin (\frac{π}{2}) : 1

sin (\frac{π}{2})

Use the following trivial identity:

sin (\frac{π}{2}) = 1

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}

= 1

= 1 \cdot sin (a)

Multiply:

1 \cdot sin (a) = sin (a)

= sin (a)

= 0 + sin (a)

0 + sin (a) = sin (a)

= sin (a)

= \frac{cos ( a )}{sin ( a )}

= \frac{cos ( a )}{sin ( a )}

= \frac{cos ( a )}{sin ( a )}

Use the basic trigonometric identity:

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

= cot (a)

We showed that the two sides could take the same form

\Rightarrow True

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Frequently Asked Questions (FAQ)

Is cot(a)=tan(pi/2-a) ?
The answer to whether cot(a)=tan(pi/2-a) is True