Thread: Related rates question!!!

Two sides of a triangle have lengths 12 m and 14 m. The angle between them is increasing at a rate of 2°/min. How fast is the length of the third side increasing when the angle between the sides of fixed length is 60°?

in this question i think i need to use the cosines law right..but how can i take the derivatives of the cosines law??

cosine law


x is angle between b and c





now substitute the value of b, c dx/dt and x (we have to find da/dt when x = 60 degree)