Express the ratios cos A, tan A and sec A in terms of sin A.

If sin 3A = cos (A - 26°), where 3A is an acute angle, find the value at A.

From a point on a bridge across a river, the angles of depression of the banks on opposite sides at the river are 30° and 45°, respectively. If the bridge is at a height at 3 m from the banks, find the width at the river.

P.T (1+tan∝tan∝tanβ)² +(tan∝-tanβ)² =sec² ∝sec²β.

\(P.T\left( \frac { 1+{ tan }^{ 2 }A }{ 1+{ cot }^{ 2 }A } \right) ={ \left( \frac { 1-tan\quad A }{ 1-cot\quad A } \right) }^{ 2 }={ tan }^{ 2 }A\)