cos a = \(\frac{15}{17}\)
∴ sin a = \(\sqrt{1-cos^2a}\)
= \(\sqrt{1-(\frac{15}{17})^2}\)
= \(\sqrt{\frac{289-225}{289}}\)
= \(\sqrt{\frac{64}{289}}\)
= \(\frac{8}{17}\).
Now,
Sin2a = 2sina.cosa
= 2 x \(\frac{8}{17}\) x \(\frac{15}{17}\)
= \(\frac{240}{289}\).