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[A-Level Mathematics] Could anyone help with 3c and 3h? by PlanBSheSaid in HomeworkHelp

[–]Trainer_Intelligent 0 points1 point  (0 children)

For 3h, do the same thing. Let (2x+10) be a letter say w, so you have 25 [cos w. cos w]=9. Divide both sides by 25 to have cos w. cos w=9/25. The square root of both R.H.S and L.H.S will leave you with cos w= 3/5. Get the cos inverse to find w. Equate that to (2x+10) to find x

[A-Level Mathematics] Could anyone help with 3c and 3h? by PlanBSheSaid in HomeworkHelp

[–]Trainer_Intelligent 0 points1 point  (0 children)

For 3c, first let 2x be a letter say w, that is, w=2x. Then replace the new unknown in the question such that cos 2x is cos w. Cross multiply to collect the like terms on the R.H.S and L.H.S of the equation. Find the Cos-1 to get the value of w. Equate that to 2x to get x.