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csc(θ)<0\land (csc(θ))(cot(θ))>0

Solution

csc (θ) < 0 and (csc (θ)) (cot (θ)) > 0

Solution

False for all θ \in R

Solution steps

csc (θ) < 0 and (csc (θ)) (cot (θ)) > 0

csc (θ) < 0 :

False for all

θ \in R

csc (θ) < 0

Express with sin, cos

csc (θ) < 0

Use the basic trigonometric identity:

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

\frac{1}{sin ( θ )} < 0

\frac{1}{sin ( θ )} < 0

\frac{1}{a} < 0

then

a < 0

sin (θ) < 0

No Solution for θ \in R

csc (θ) cot (θ) > 0 : 2 πn < θ < \frac{π}{2} + 2 πn or \frac{3 π}{2} + 2 πn < θ < 2 π + 2 πn

csc (θ) cot (θ) > 0

Periodicity of

csc (θ) cot (θ) : 2 π

csc (θ) cot (θ)

is composed of the following functions and periods:

csc (θ)

with periodicity of

2 π

The compound periodicity is:

= 2 π

Express with sin, cos

csc (θ) cot (θ) > 0

Use the basic trigonometric identity:

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

\frac{1}{sin ( θ )} cot (θ) > 0

Use the basic trigonometric identity:

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

\frac{1}{sin ( θ )} \cdot \frac{cos ( θ )}{sin ( θ )} > 0

\frac{1}{sin ( θ )} \cdot \frac{cos ( θ )}{sin ( θ )} > 0

Simplify

\frac{1}{sin ( θ )} \cdot \frac{cos ( θ )}{sin ( θ )} : \frac{cos ( θ )}{sin ^{2} ( θ )}

\frac{1}{sin ( θ )} \cdot \frac{cos ( θ )}{sin ( θ )}

Multiply fractions:

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

= \frac{1 \cdot cos ( θ )}{sin ( θ ) sin ( θ )}

Multiply:

1 \cdot cos (θ) = cos (θ)

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

sin (θ) sin (θ) = sin^{2} (θ)

sin (θ) sin (θ)

Apply exponent rule:

a^{b} \cdot a^{c} = a^{b + c}

sin (θ) sin (θ) = sin^{1 + 1} (θ)

= sin^{1 + 1} (θ)

Add the numbers:

1 + 1 = 2

= sin^{2} (θ)

= \frac{cos ( θ )}{sin ^{2} ( θ )}

\frac{cos ( θ )}{sin ^{2} ( θ )} > 0

Find the zeroes and undifined points of

\frac{cos ( θ )}{sin ^{2} ( θ )}

for

0 \leq θ < 2 π

To find the zeroes, set the inequality to zero

\frac{cos ( θ )}{sin ^{2} ( θ )} = 0

\frac{cos ( θ )}{sin ^{2} ( θ )} = 0, 0 \leq θ < 2 π : θ = \frac{π}{2}, θ = \frac{3 π}{2}

\frac{cos ( θ )}{sin ^{2} ( θ )} = 0, 0 \leq θ < 2 π

\frac{f ( x )}{g ( x )} = 0 \Rightarrow f (x) = 0

cos (θ) = 0

General solutions for

cos (θ) = 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}

θ = \frac{π}{2} + 2 πn, θ = \frac{3 π}{2} + 2 πn

θ = \frac{π}{2} + 2 πn, θ = \frac{3 π}{2} + 2 πn

Solutions for the range

0 \leq θ < 2 π

θ = \frac{π}{2}, θ = \frac{3 π}{2}

Find the undefined points:

θ = 0, θ = π

Find the zeros of the denominator

sin^{2} (θ) = 0

Apply rule

x^{n} = 0 \Rightarrow x = 0

sin (θ) = 0

General solutions for

sin (θ) = 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}

θ = 0 + 2 πn, θ = π + 2 πn

θ = 0 + 2 πn, θ = π + 2 πn

Solve

θ = 0 + 2 πn : θ = 2 πn

θ = 0 + 2 πn

0 + 2 πn = 2 πn

θ = 2 πn

θ = 2 πn, θ = π + 2 πn

Solutions for the range

0 \leq θ < 2 π

θ = 0, θ = π

0, \frac{π}{2}, π, \frac{3 π}{2}

Identify the intervals

0 < θ < \frac{π}{2}, \frac{π}{2} < θ < π, π < θ < \frac{3 π}{2}, \frac{3 π}{2} < θ < 2 π

Summarize in a table:

cos (θ) sin^{2} (θ) \frac{c o s ( θ )}{s i n ^{2} ( θ )} θ = 0 + 0 Undefined 0 < θ < \frac{π}{2} + + + θ = \frac{π}{2} 0 + 0 \frac{π}{2} < θ < π - + - θ = π - 0 Undefined π < θ < \frac{3 π}{2} - + - θ = \frac{3 π}{2} 0 + 0 \frac{3 π}{2} < θ < 2 π + + + θ = 2 π + 0 Undefined

Identify the intervals that satisfy the required condition:

> 0

0 < θ < \frac{π}{2} or \frac{3 π}{2} < θ < 2 π

Apply the periodicity of

csc (θ) cot (θ)

2 πn < θ < \frac{π}{2} + 2 πn or \frac{3 π}{2} + 2 πn < θ < 2 π + 2 πn

Combine the intervals

False for all θ \in R and (2 πn < θ < \frac{π}{2} + 2 πn or \frac{3 π}{2} + 2 πn < θ < 2 π + 2 πn)

Merge Overlapping Intervals

False for all θ \in R

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