In The Mountains

At the foot of a mountain, the elevation of its summit is 45^@ . After ascending 2 km towards the mountain upon an incline of 30^@ , the elevation changes to 60^@ . The height of the mountain is

At the foot of the mountain the elevation of its summit is 45^(@) After ascnding 100 mt towards the mountain up a slope of 30^(@) inclination is found to be 60^(@) . The height of the mountain is

The mountaineers carry oxygen with them because: