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Popular >

10sin(x)cos^2(x)+3cos(x)=0

Solution

10 sin (x) cos^{2} (x) + 3 cos (x) = 0

Solution

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn, x = - \frac{0.64350 \dots}{2} + πn, x = \frac{π}{2} + \frac{0.64350 \dots}{2} + πn

Degrees

x = 9 0^{\circ} + 36 0^{\circ} n, x = 27 0^{\circ} + 36 0^{\circ} n, x = - 18.43494 \dots^{\circ} + 18 0^{\circ} n, x = 108.43494 \dots^{\circ} + 18 0^{\circ} n

Solution steps

10 sin (x) cos^{2} (x) + 3 cos (x) = 0

Factor

10 sin (x) cos^{2} (x) + 3 cos (x) : cos (x) (10 sin (x) cos (x) + 3)

10 sin (x) cos^{2} (x) + 3 cos (x)

Apply exponent rule:

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

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

= 10 cos (x) cos (x) + 3 cos (x)

Factor out common term

cos (x)

= cos (x) (10 sin (x) cos (x) + 3)

cos (x) (10 sin (x) cos (x) + 3) = 0

Solving each part separately

cos (x) = 0 or 10 sin (x) cos (x) + 3 = 0

cos (x) = 0 : x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn

cos (x) = 0

General solutions for

cos (x) = 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}

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

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

10 sin (x) cos (x) + 3 = 0 : x = - \frac{arcsin ( \frac{3}{5} )}{2} + πn, x = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + πn

10 sin (x) cos (x) + 3 = 0

Rewrite using trig identities

10 sin (x) cos (x) + 3

Use the Double Angle identity:

2 sin (x) cos (x) = sin (2 x)

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

= 3 + 10 \cdot \frac{sin ( 2 x )}{2}

3 + 10 \cdot \frac{sin ( 2 x )}{2} = 0

10 \cdot \frac{sin ( 2 x )}{2} = 5 sin (2 x)

10 \cdot \frac{sin ( 2 x )}{2}

Multiply fractions:

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

= \frac{sin ( 2 x ) \cdot 10}{2}

Divide the numbers:

\frac{10}{2} = 5

= 5 sin (2 x)

3 + 5 sin (2 x) = 0

Move

3

to the right side

3 + 5 sin (2 x) = 0

Subtract

3

from both sides

3 + 5 sin (2 x) - 3 = 0 - 3

Simplify

5 sin (2 x) = - 3

5 sin (2 x) = - 3

Divide both sides by

5

5 sin (2 x) = - 3

Divide both sides by

5

\frac{5 sin ( 2 x )}{5} = \frac{- 3}{5}

Simplify

sin (2 x) = - \frac{3}{5}

sin (2 x) = - \frac{3}{5}

Apply trig inverse properties

sin (2 x) = - \frac{3}{5}

General solutions for

sin (2 x) = - \frac{3}{5}

sin (x) = - a \Rightarrow x = arcsin (- a) + 2 πn, x = π + arcsin (a) + 2 πn

2 x = arcsin (- \frac{3}{5}) + 2 πn, 2 x = π + arcsin (\frac{3}{5}) + 2 πn

2 x = arcsin (- \frac{3}{5}) + 2 πn, 2 x = π + arcsin (\frac{3}{5}) + 2 πn

Solve

2 x = arcsin (- \frac{3}{5}) + 2 πn : x = - \frac{arcsin ( \frac{3}{5} )}{2} + πn

2 x = arcsin (- \frac{3}{5}) + 2 πn

Simplify

arcsin (- \frac{3}{5}) + 2 πn : - arcsin (\frac{3}{5}) + 2 πn

arcsin (- \frac{3}{5}) + 2 πn

Use the following property:

arcsin (- x) = - arcsin (x)

arcsin (- \frac{3}{5}) = - arcsin (\frac{3}{5})

= - arcsin (\frac{3}{5}) + 2 πn

2 x = - arcsin (\frac{3}{5}) + 2 πn

Divide both sides by

2

2 x = - arcsin (\frac{3}{5}) + 2 πn

Divide both sides by

2

\frac{2 x}{2} = - \frac{arcsin ( \frac{3}{5} )}{2} + \frac{2 πn}{2}

Simplify

x = - \frac{arcsin ( \frac{3}{5} )}{2} + πn

x = - \frac{arcsin ( \frac{3}{5} )}{2} + πn

Solve

2 x = π + arcsin (\frac{3}{5}) + 2 πn : x = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + πn

2 x = π + arcsin (\frac{3}{5}) + 2 πn

Divide both sides by

2

2 x = π + arcsin (\frac{3}{5}) + 2 πn

Divide both sides by

2

\frac{2 x}{2} = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + \frac{2 πn}{2}

Simplify

x = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + πn

x = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + πn

x = - \frac{arcsin ( \frac{3}{5} )}{2} + πn, x = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + πn

Combine all the solutions

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn, x = - \frac{arcsin ( \frac{3}{5} )}{2} + πn, x = \frac{π}{2} + \frac{arcsin ( \frac{3}{5} )}{2} + πn

Show solutions in decimal form

x = \frac{π}{2} + 2 πn, x = \frac{3 π}{2} + 2 πn, x = - \frac{0.64350 \dots}{2} + πn, x = \frac{π}{2} + \frac{0.64350 \dots}{2} + πn

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