What is $$\sin (\alpha + \beta ) - 2sin\alpha cos\beta + sin(\alpha - \beta )$$ equal to?

If $$\cos ec\theta = {{29} \over {21}}$$, where 0 < $$\theta$$ < 90$$^\circ$$, then what is the value of 4 sec$$\theta$$ + 4 tan$$\theta$$ ?

Consider the following statements

1. cos $$\theta$$ + sec $$\theta$$ can never be equal to 1.5 .

2. tan $$\theta$$ + cot $$\theta$$ can never be less than 2 .

Which of the above statements is/are correct?

What is the length of the chord of a unit circle which subtends an angle $$\theta$$ at the centre?