Prove that: cos2pi/7+cos4pi/7+cos8pi/7=-1/2

Find an equation of the line perpendicular to the graph of 28x-7y=9 that passes through the point at (4,1)

In the field of thermodynamics, rankine is the unit used to measure temperature. one can convert temperature from celsius into rankine using the formula , what is the temperature in celsius corresponding to r degrees rankine? a. 9/5(c - 273) b. 9/5(c + 273) c. 5/9( c - 273) d. 5/9( c + 273)

The length of a rectangle plus its width is 24 cm. the area is 143 square cm. what are the length and width of the rectangle?