Question

T1 cos30=T2 cos60
=???
​

Answer 1

Resolving T1 and T2 vertically in the diagram above:

T1 sin30 + T2 sin60 = W = mg

Alternatively, we could resolve T1 and T2 horizontally.

Since there is no horizontal motion:

Forces left = Forces right

Resolving T1 and T2 horizontally in the diagram above:

T1 cos30 = T2 cos60

Note that the vertical weight force W (= mg) when resolved horizontally equals zero

(W × cos 90 = 0).