Trigonometry - Symmetry of Trigonometric Functions

Trigonometry - Symmetry of Trigonometric Functions

TGM Original Questions

It is given that \(\sin 25^\circ = \frac{a}{b}\). Express each of the following in terms of \(a\) and \(b\).

  1. \(\sin 25^\circ + \sin 45^\circ + \sin 65^\circ\)
  2. \(\cos 25^\circ + \cos 45^\circ + \cos 65^\circ\)
  3. \(\tan 205^\circ + \tan 225^\circ + \tan 245^\circ\)
  4. \(\sec (-25^\circ) + \sec (-45^\circ) + \sec (-65^\circ)\)

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Answer:(i) \(\dfrac{a + \sqrt{b^2 - a^2}}{b} + \dfrac{\sqrt{2}}{2}\); (ii) \(\dfrac{a + \sqrt{b^2 - a^2}}{b} + \dfrac{\sqrt{2}}{2}\); (iii) \(1 + \dfrac{b^2}{a \sqrt{b^2 - a^2}}\); (iv) \(\sqrt{2} + \dfrac{b(a + \sqrt{b^2 - a^2})}{a \sqrt{b^2 - a^2}}\)

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