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X-coordinate of Trigonometric Functions (1 Viewer)
- Thread starter BlueGas
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They divided both sides by cos x so that they could get the equation tan x = 1, which is easy to solve. Subtracting cos x from both sides wouldn't really help as much with solving the equation.Can someone explain to me the working out of question 9. a)? When sinx = cosx, why did they divide sinx by cosx? Shouldn't they minus cosx to the other side?
BlueGas
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Are you actually allowed to do that? Because when it comes to normal algebra you would usually minus to find x.
integral95
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In solving (x-1)² = 2(x-1), you CAN'T divide by (x-1) because x=1 is a zero of BOTH the LHS and RHS, and hence a solution of the equation, so that solution is lost in doing the division.
When solving sinx = cosx, you CAN divide by cosx because there are NO values of x for which sinx and cosx are BOTH zero.
So even though the zeros of cosx will lost by dividing, those zeros won't be solutions of the equation.
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