What is the general solution for cos(x+25)sec(65-x)=1 ?

The general solution for cos(x+25)sec(65-x)=1 is x=20-180n

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cos(x+25)sec(65-x)=1

Solution

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x) = 1

Solution

x = 2 0^{\circ} - 18 0^{\circ} n

Radians

x = \frac{π}{9} - πn

Solution steps

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x) = 1

Subtract

1

from both sides

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x) - 1 = 0

Simplify

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x) - 1 : cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{234 0 ^{\circ} - 36 x}{36}) - 1

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x) - 1

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x) = cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{234 0 ^{\circ} - 36 x}{36})

cos (x + 2 5^{\circ}) sec (6 5^{\circ} - x)

Join

x + 2 5^{\circ} : \frac{36 x + 90 0 ^{\circ}}{36}

x + 2 5^{\circ}

Convert element to fraction:

x = \frac{x 36}{36}

= \frac{x \cdot 36}{36} + 2 5^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{x \cdot 36 + 90 0 ^{\circ}}{36}

= cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (- x + 6 5^{\circ})

Join

6 5^{\circ} - x : \frac{234 0 ^{\circ} - 36 x}{36}

6 5^{\circ} - x

Convert element to fraction:

x = \frac{x 36}{36}

= 6 5^{\circ} - \frac{x \cdot 36}{36}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{234 0 ^{\circ} - x \cdot 36}{36}

= cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{- 36 x + 234 0 ^{\circ}}{36})

= cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{- 36 x + 234 0 ^{\circ}}{36}) - 1

cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{234 0 ^{\circ} - 36 x}{36}) - 1 = 0

Rewrite using trig identities

- 1 + cos (\frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{234 0 ^{\circ} - 36 x}{36})

Use the following identity:

cos (x) = sin (9 0^{\circ} - x)

= - 1 + sin (9 0^{\circ} - \frac{36 x + 90 0 ^{\circ}}{36}) sec (\frac{234 0 ^{\circ} - 36 x}{36})

Join

9 0^{\circ} - \frac{36 x + 90 0 ^{\circ}}{36} : \frac{- 36 x + 234 0 ^{\circ}}{36}

9 0^{\circ} - \frac{36 x + 90 0 ^{\circ}}{36}

Least Common Multiplier of

2, 36 : 36

2, 36

Least Common Multiplier (LCM)

Prime factorization of

2 : 2

2

2

is a prime number, therefore no factorization is possible

= 2

Prime factorization of

36 : 2 \cdot 2 \cdot 3 \cdot 3

36

36

divides by

236 = 18 \cdot 2

= 2 \cdot 18

18

divides by

218 = 9 \cdot 2

= 2 \cdot 2 \cdot 9

9

divides by

39 = 3 \cdot 3

= 2 \cdot 2 \cdot 3 \cdot 3

2, 3

are all prime numbers, therefore no further factorization is possible

= 2 \cdot 2 \cdot 3 \cdot 3

Multiply each factor the greatest number of times it occurs in either

2

36

= 2 \cdot 2 \cdot 3 \cdot 3

Multiply the numbers:

2 \cdot 2 \cdot 3 \cdot 3 = 36

= 36

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

36

For

9 0^{\circ} :

multiply the denominator and numerator by

18

9 0^{\circ} = \frac{18 0 ^{\circ} 18}{2 \cdot 18} = 9 0^{\circ}

= 9 0^{\circ} - \frac{36 x + 90 0 ^{\circ}}{36}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{18 0 ^{\circ} 18 - ( 36 x + 90 0 ^{\circ} )}{36}

Expand

18 0^{\circ} 18 - (36 x + 90 0^{\circ}) : - 36 x + 234 0^{\circ}

18 0^{\circ} 18 - (36 x + 90 0^{\circ})

= 324 0^{\circ} - (36 x + 90 0^{\circ})

- (36 x + 90 0^{\circ}) : - 36 x - 90 0^{\circ}

- (36 x + 90 0^{\circ})

Distribute parentheses

= - (36 x) - (90 0^{\circ})

Apply minus-plus rules

+ (- a) = - a

= - 36 x - 90 0^{\circ}

= 18 0^{\circ} 18 - 36 x - 90 0^{\circ}

Simplify

18 0^{\circ} 18 - 36 x - 90 0^{\circ} : - 36 x + 234 0^{\circ}

18 0^{\circ} 18 - 36 x - 90 0^{\circ}

Group like terms

= - 36 x + 324 0^{\circ} - 90 0^{\circ}

Add similar elements:

324 0^{\circ} - 90 0^{\circ} = 234 0^{\circ}

= - 36 x + 234 0^{\circ}

= - 36 x + 234 0^{\circ}

= \frac{- 36 x + 234 0 ^{\circ}}{36}

= - 1 + sin (\frac{- 36 x + 234 0 ^{\circ}}{36}) sec (\frac{234 0 ^{\circ} - 36 x}{36})

sec (\frac{234 0 ^{\circ} - 36 x}{36}) sin (\frac{234 0 ^{\circ} - 36 x}{36}) = tan (\frac{234 0 ^{\circ} - 36 x}{36})

sec (\frac{234 0 ^{\circ} - 36 x}{36}) sin (\frac{234 0 ^{\circ} - 36 x}{36})

Express with sin, cos

sec (\frac{234 0 ^{\circ} - 36 x}{36}) sin (\frac{234 0 ^{\circ} - 36 x}{36})

Use the basic trigonometric identity:

sec (\frac{234 0 ^{\circ} - 36 x}{36}) = \frac{1}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )}

= \frac{1}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )} sin (\frac{234 0 ^{\circ} - 36 x}{36})

Simplify

\frac{1}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )} sin (\frac{234 0 ^{\circ} - 36 x}{36}) : \frac{sin ( \frac{234 0 ^{\circ} - 36 x}{36} )}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )}

\frac{1}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )} sin (\frac{234 0 ^{\circ} - 36 x}{36})

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= \frac{1 sin ( \frac{234 0 ^{\circ} - 36 x}{36} )}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )}

Multiply:

1 \cdot sin (\frac{234 0 ^{\circ} - 36 x}{36}) = sin (\frac{234 0 ^{\circ} - 36 x}{36})

= \frac{sin ( \frac{234 0 ^{\circ} - 36 x}{36} )}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )}

= \frac{sin ( \frac{234 0 ^{\circ} - 36 x}{36} )}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )}

= \frac{sin ( \frac{234 0 ^{\circ} - 36 x}{36} )}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )}

Use the basic trigonometric identity:

\frac{sin ( \frac{234 0 ^{\circ} - 36 x}{36} )}{cos ( \frac{234 0 ^{\circ} - 36 x}{36} )} = tan (\frac{234 0 ^{\circ} - 36 x}{36})

= tan (\frac{234 0 ^{\circ} - 36 x}{36})

= - 1 + tan (\frac{234 0 ^{\circ} - 36 x}{36})

- 1 + tan (\frac{234 0 ^{\circ} - 36 x}{36}) = 0

Move

1

to the right side

- 1 + tan (\frac{234 0 ^{\circ} - 36 x}{36}) = 0

Add

1

to both sides

- 1 + tan (\frac{234 0 ^{\circ} - 36 x}{36}) + 1 = 0 + 1

Simplify

tan (\frac{234 0 ^{\circ} - 36 x}{36}) = 1

tan (\frac{234 0 ^{\circ} - 36 x}{36}) = 1

General solutions for

tan (\frac{234 0 ^{\circ} - 36 x}{36}) = 1

tan (x)

periodicity table with

18 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} tan (x) 0 \frac{3}{3} 13 \pm \infty - 3 - 1 - \frac{3}{3}

\frac{234 0 ^{\circ} - 36 x}{36} = 4 5^{\circ} + 18 0^{\circ} n

\frac{234 0 ^{\circ} - 36 x}{36} = 4 5^{\circ} + 18 0^{\circ} n

Solve

\frac{234 0 ^{\circ} - 36 x}{36} = 4 5^{\circ} + 18 0^{\circ} n : x = 2 0^{\circ} - 18 0^{\circ} n

\frac{234 0 ^{\circ} - 36 x}{36} = 4 5^{\circ} + 18 0^{\circ} n

Multiply both sides by

36

\frac{234 0 ^{\circ} - 36 x}{36} = 4 5^{\circ} + 18 0^{\circ} n

Multiply both sides by

36

\frac{36 ( 234 0 ^{\circ} - 36 x )}{36} = 36 \cdot 4 5^{\circ} + 648 0^{\circ} n

Simplify

\frac{36 ( 234 0 ^{\circ} - 36 x )}{36} = 36 \cdot 4 5^{\circ} + 648 0^{\circ} n

Simplify

\frac{36 ( 234 0 ^{\circ} - 36 x )}{36} : 234 0^{\circ} - 36 x

\frac{36 ( 234 0 ^{\circ} - 36 x )}{36}

Divide the numbers:

\frac{36}{36} = 1

= 234 0^{\circ} - 36 x

Simplify

36 \cdot 4 5^{\circ} + 648 0^{\circ} n : 162 0^{\circ} + 648 0^{\circ} n

36 \cdot 4 5^{\circ} + 648 0^{\circ} n

36 \cdot 4 5^{\circ} = 162 0^{\circ}

36 \cdot 4 5^{\circ}

Multiply fractions:

a \cdot \frac{b}{c} = \frac{a \cdot b}{c}

= 162 0^{\circ}

Divide the numbers:

\frac{36}{4} = 9

= 162 0^{\circ}

= 162 0^{\circ} + 648 0^{\circ} n

234 0^{\circ} - 36 x = 162 0^{\circ} + 648 0^{\circ} n

234 0^{\circ} - 36 x = 162 0^{\circ} + 648 0^{\circ} n

234 0^{\circ} - 36 x = 162 0^{\circ} + 648 0^{\circ} n

Move

234 0^{\circ}

to the right side

234 0^{\circ} - 36 x = 162 0^{\circ} + 648 0^{\circ} n

Subtract

234 0^{\circ}

from both sides

234 0^{\circ} - 36 x - 234 0^{\circ} = 162 0^{\circ} + 648 0^{\circ} n - 234 0^{\circ}

Simplify

- 36 x = - 72 0^{\circ} + 648 0^{\circ} n

- 36 x = - 72 0^{\circ} + 648 0^{\circ} n

Divide both sides by

- 36

- 36 x = - 72 0^{\circ} + 648 0^{\circ} n

Divide both sides by

- 36

\frac{- 36 x}{- 36} = - \frac{72 0 ^{\circ}}{- 36} + \frac{648 0 ^{\circ} n}{- 36}

Simplify

\frac{- 36 x}{- 36} = - \frac{72 0 ^{\circ}}{- 36} + \frac{648 0 ^{\circ} n}{- 36}

Simplify

\frac{- 36 x}{- 36} : x

\frac{- 36 x}{- 36}

Apply the fraction rule:

\frac{- a}{- b} = \frac{a}{b}

= \frac{36 x}{36}

Divide the numbers:

\frac{36}{36} = 1

= x

Simplify

- \frac{72 0 ^{\circ}}{- 36} + \frac{648 0 ^{\circ} n}{- 36} : 2 0^{\circ} - 18 0^{\circ} n

- \frac{72 0 ^{\circ}}{- 36} + \frac{648 0 ^{\circ} n}{- 36}

\frac{72 0 ^{\circ}}{- 36} = - 2 0^{\circ}

\frac{72 0 ^{\circ}}{- 36}

Apply the fraction rule:

\frac{a}{- b} = - \frac{a}{b}

= - 2 0^{\circ}

Cancel the common factor:

4

= - 2 0^{\circ}

\frac{648 0 ^{\circ} n}{- 36} = - 18 0^{\circ} n

\frac{648 0 ^{\circ} n}{- 36}

Apply the fraction rule:

\frac{a}{- b} = - \frac{a}{b}

= - \frac{648 0 ^{\circ} n}{36}

Divide the numbers:

\frac{36}{36} = 1

= - 18 0^{\circ} n

= - (- 2 0^{\circ}) - 18 0^{\circ} n

Apply rule

- (- a) = a

= 2 0^{\circ} - 18 0^{\circ} n

x = 2 0^{\circ} - 18 0^{\circ} n

x = 2 0^{\circ} - 18 0^{\circ} n

x = 2 0^{\circ} - 18 0^{\circ} n

x = 2 0^{\circ} - 18 0^{\circ} n

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Frequently Asked Questions (FAQ)

What is the general solution for cos(x+25)sec(65-x)=1 ?
The general solution for cos(x+25)sec(65-x)=1 is x=20-180n