If A=(1,1) ,B=(4,5) and C=(6,13) then cos A=

In ΔABC , if A=75⁰, B=45⁰, C=√3, then b=

In ΔABC, if a(b cos C + c cos B) =2ka², then k =

In ΔABC, R² (sin 2A+sin 2B+sin 2C)=

In ΔABC, if cos² A+cos²B+ cos²C=3/4, then the triangle is

The angle of elevation of the summit of a mountain at a point A is 45⁰. After walking 200 mt from A towards the mountain along a road included at 15⁰, it is observed that the angle of elevation of the summit is 60⁰. The height of the mountain is

In ΔABC, if sin A: sin C = sin (A-B) :sin (B-C), then a²,b²,c² are in

In a triangle ABC, (a²-b²-c²) tan A+ (a²-b²+c²) tan B is equal to

In ΔABC, r₁²+r₂²+r₃²+r² =

A man observes that angle of elevation of the top of a tower from a point P on the ground is θ. He moves a certain distance towards the foot of the tower and finds that the angle of elevation of the top has doubled. He further moves a distance 3/4 of the previous and finds that the angle of elevation is three times that at P. Then angle θ is given by