Wats -720sin¥ - 1800cos¥ = 540 find ¥?

I've never worked with "yens" (the Japanese dollar) before, so I'll use θ instead:

... -720 sin(θ) - 1800cos(θ) = 540

or -720 sin(θ) - 1800 √ (1 - sin²(θ) ) = 540

or √(1 - sin²(θ) ) = - ( 540/1800 + 720/1800 sin(θ) )

or 1 - sin²(θ) = (- .3 - .4 sin(θ) )²

or 1 - sin²(θ) = .16 sin²(θ) + .24 sin(θ) + .09

or 1.16 sin²(θ) + .24 sin(θ) - .91 = 0

or 1.16 ( sin(θ) - .788283) ( sin(θ) + .995179 )

or θ = { arcsin(.788283), arcsin(-.995179) }