Question

how to find length of altitude from a to bc​

Answer 1

it's right angle triangle so we can you Pythagoras theorem to find BC

${bc}^{2} = {ac}^{2} + {ab}^{2} \\ {bc}^{2} = {4}^{2} + {3}^{2} \\ {bc}^{2} = 16 + 9 \\ bc = \sqrt{25} \\ bc = 5$