[" Amereat of "780" : "],[[1.," in "^(-1)(-(1)/(2))," 2."cos^(-1)((sqrt(3))/(2))]]

cot780^(@)=cot(2xx360^(@)+60^(@)) =cot60^(@)=(1)/(sqrt(3))

Suppose the bent part of the frame of the previous problem has a thermal conductivity of 780s^(-1)m^(-1) ^(@)C^(-1) whereas it is 390Js^(-1)m^(-1) ^(@)C^(-1) for the staight the bent part to the rate of heat flow through the staight part.

Suppose the bent part of the frame of the previous problem has a thermal conductivity of 780s^(-1)m^(-1).^(@)C^(-1) whereas it is 390Js^(-1)m^(-1).^(@)C^(-1) for the straight the bent part to the rate of heat flow through the straight part.

Prove that: sin780^(@)s in120^(@)+cos240^(@)sin390^(@)=(1)/(2)

Prove that: s in780^(@)s in480^(@)+cos120^(@)s in150^(@)=(1)/(2)

Prove that sin 780^(@) sin 480^(@)+cos240^(@). Cos300^(@) = 1/2

Prove that sin780^(@)*sin480^(@)+cos120^(@)*sin150^(@)=(1)/(2)

Prove that: sin 780^0sin 480^0+cos 120^0sin 150^0=1/2

156 468 780 1094 1404 1716

The number of points,having both co- ordinates as integers,that lie in the interior of the triangle with vertices (0,0),(0,41) and (41,0) is (1)901 (2) 861 (3) 820 (4) 780 .