In which of the following situations

MATHEMATICS · Single correct · A Level · Mathematics · Trigonometry · Trigonometry

Problem

In which of the following situations, it is possible to have a

\Delta ABC

? (All symbols used have usual meaning in a triangle) (1)

(a + c - b)(a - c + b) = 4bc

(2)

b^2 \sin 2C + \cos^2 2B = ab

(3)

a = 3, b = 5, c = 7

and

C = \frac{2\pi}{3}

(4)

\cos\left(\frac{A-C}{2}\right) = \cos\left(\frac{A+C}{2}\right)