If sin =1/2then show that 3cos -4cos^3=0

Step-by-step explanation:

sen(x)=0.5

3cos(x)-4cos^3(x)=0

Remember:

cos^3(x)=cos(x)*cos^2(x)

3cos(x)-4(cos(x)*cos^2(x))=0

we have :

cos^2(x)=1-sin^2(x)

Then:

3cos(x)-4(cos(x)*(1-sin^2(x)))=0

sin^2(x)=(0.5)^2=0.25

3cos(x)-4(cos(x)*(1-0.25))=0

3cos(x)-4(cos(x)*(0.75))=0

Finally

3cos(x)-3cos(x)=0

-2x + 7 = 7

subtract 7 from both sides.

-2x = 0

divide both sides by -2.

x = 0

answer:

total cost for tiles and paints is $924.  

step-by-step explanation:

we have been given that a community hall is in the shape of a cuboid. the hall is 40m long 15m high and 3m wide.

the paint will be required for 4 walls and ceiling.

let us find area of walls and ceiling.

therefore, the area of walls and ceiling is 1410 square meters.

given: cost for 10 litre of paint is $10 and 10 litre paint covers 25 square meter. therefore,

therefore, the total painting cost is $564.

tiles will be required for floor. let us find the area of floor.

given: 1m squared floor tiles costs $3. so,

therefore, the total tiles cost is $360.

now let us find combined total cost of tiles and paint.

therefore, the combined total cost of tiles and paint is $924.