We start with the equation 8cosθ+15sinθ=15. We need to find 15cosθ−8sinθ, which we will denote as t.First, consider squaring both sides of the given expression for clarity:Start with (8cosθ+15sinθ)2=152 :64cos2θ+225sin2θ+2⋅8⋅15cosθsinθ=225.Simplify to:64cos2θ+225sin2θ+240cosθsinθ=225.For t=15cosθ−8sinθ, square both sides:(15cosθ−8sinθ)2=t2.Expanding this gives:225cos2θ+64sin2θ−240cosθsinθ=t2.Now, add the two squared expressions:64cos2θ+225sin2θ+240cosθsinθ+225cos2θ+64sin2θ−240cosθsinθ=225Simplify the combined expression:289(cos2θ+sin2θ)=225+t2.Since cos2θ+sin2θ=1, it follows that:289=225+t2.Solve for t2 :289−225=t264=t2t=8Thus, 15cosθ−8sinθ=8.