In `triangleABC` ,`Delta=6`, `abc=60`, `r=1` Then the value of `1/a+1/b+1/c` is nearly (a) 0.5 (b) 0.6 (c) 0.4 (d) 0.8

If (21. 4)^a=(0. 00214)^b=100 , then the value of 1/a-1/b is 0 (b) 1 (c) 2 (d) 4

The value of sum_(r=0)^(10)cos^3((rpi)/3) is equal to (a) 1/4 (b) 1/8 (c) -1/4 (d) -1/8

The value of tan6^0tan42^0tan66^0tan78^0 is (a)1 (b) 1/2 (c) 1/4 (d) 1/8

Let A B C be a triangle. Let A be the point (1,2),y=x be the perpendicular bisector of A B , and x-2y+1=0 be the angle bisector of /_C . If the equation of B C is given by a x+b y-5=0 , then the value of a+b is (a) 1 (b) 2 (c) 3 (d) 4

If in a triangle A B C ,/_C=60^0, then prove that 1/(a+c)+1/(b+c)=3/(a+b+c) .

In a triangle A B C ,/_A=60^0a n db : e=(sqrt(3)+1):2, then find the value of (/_B-/_C)dot

In triangle ABC, if A-B=120^@ and R=8r, where R and r have their usual meanings, then cos C equal (a) 3/4 (b) 2/3 (c) 5/6 (d) 7/8

Find the value of a if [a-b2a+c2a-b3c+d]=[-1 5 0 13]

In A B C , if (sinA)/(csinB)+(sinB)/c+(sinC)/b=c/(a b)+b/(a c)+a/(b c), then the value of angle A is 120^0 (b) 90^0 (c) 60^0 (d) 30^0

In triangle A B C ,/_A=60^0,/_B=40^0,a n d/_C=80^0dot If P is the center of the circumcircle of triangle A B C with radius unity, then the radius of the circumcircle of triangle B P C is (a)1 (b) sqrt(3) (c) 2 (d) sqrt(3) 2