已知∠1+∠2+∠3=180°,∠1=30°,∠2=90°,求∠3.
∠3=180°-∠1-∠2
=180°-30°-90°
=60°
答:∠3是60°.
Jim is always going to sleep with his bedroom light ______.[ ]
A.on
B.with
C.in
D.by
河流相的沉积特征有哪些?