Vivek singh
Last Activity: 7 Years ago
**cos C=tan A****so tan C=sqrt(1-tan ^2 A)/tan A****cos B=tan C=sqrt(1-tan ^2 A)/tan A****so tan B=sqrt((2×tan ^2 A-1)/(1-tan ^2 A))****But cos A=tan B****cos A=sqrt(2×tan ^2 A-1)/(1-tan ^2 A))****cos ^2 A=(2×tan ^2 A-1)/(1-tan ^2 A)****1/sec ^2 A=**(**2×tan ^2 A-1)/(1-tan ^2 A)****1/(1+tan ^2 A)=(2×tan ^2 A-1)/(1-tan ^2 A)****tan ^4 A +tan ^2 A -1=0****tan ^2 A=(-1+√5)/2****cot ^2 A=2/(√5 -1)****cosec ^2 A -1 =2/(√5 -1)****cosec ^2 A=(1+√5)/(√5 -1)****sin ^2 A=(√5–1)/(√5+1)=(√5–1)^2/(√5+1)(√5–1)****sin ^2 A=((√5–1)^2)/4****sin A=(√5–1)/2.**