To find the missing angle $\angle 1$ in a triangle, we can use the fact that the sum of all angles in any triangle is always $180^\circ$.

Given:

• One angle is $40^\circ$,
• Another angle is $70^\circ$,
• Let the missing angle be $\angle 1$.

We use the formula: $\angle 1 = 180^\circ - (40^\circ + 70^\circ)$ $\angle 1 = 180^\circ - 110^\circ = 70^\circ$

So, $\angle 1 = 70^\circ$.

Would you like more details on the calculation? Here are some related questions:

1. Why do the angles of a triangle always add up to 180 degrees?
2. What is the relationship between angles in different types of triangles (e.g., equilateral, isosceles)?
3. How do supplementary angles relate to triangles?
4. Can you solve for missing angles in quadrilaterals similarly?
5. How can exterior angles of a triangle help in finding interior angles?

Tip: Always double-check your angle sums when solving for missing angles in triangles!