Area of Triangle help?

Refer to the figure below.

m∠I + m∠T + m∠R = 180°
m∠I + 105° + 30° = 180°
m∠I = 45°

IR / sin∠T = TR / sin∠I
IR / sin105 = (10 cm) / sin45°
IR = 10 × (sin105°/sin45°) cm
IR = 13.66 cm

Area of ΔTRI
= (1/2) × IR × TR × sin∠R
= (1/2) × 13.66 × 10 × sin30° cm²
= 34.2 cm²

use sine law to find the side lengths , then s = boundary / 2 & A = √ { s (s-1st side)(s-2nd side )(s-3rd side) }