Use derivative

9. The angle of elevation of the sun is decreasing at 3 rad/h. How fast is the shadow cast by a tree 10 m tall lengthening when the angle of elevation of the sun is * rad? de 2+ 10 = =- 3 rad/h tan B = -- 10m di ( tand ) = ( x ) sec's . do - 10 dx 10 O d do x 2 X SecA