# Tangent Line to f(x) Without Specified Point

1. Aug 10, 2012

### johnstobbart

1. The problem statement, all variables and given/known data

Hello again.

The question asks me to find an equation of the tangent to the graph:

$$f(x)= - sin^2 x + 1/2, x \epsilon [0, \frac{\pi}{2}$$

which makes an angle of 135° with the x-axis (measure anti-clockwise from the positive x-axis). Assume that the scales along the x- and y- axis are the same.

I just don't know how to find the point.

2. Relevant equations

3. The attempt at a solution

What I did was took the 135° value from the unit circle, which I think is:
$$\frax{3\pi}{4}$$
and worked with that as my x-coordinate.

The problem is that the question states that x ε [0, ∏/2], which means that 3∏/4 can't be x.

The only other value I can think of getting is:
√2/2 from sin(2∏ - 3∏/4).

What am I overlooking?

2. Aug 10, 2012

### Simon Bridge

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