त्रिकोणमितीय अनुपातों को सीखने के लिए छात्रों द्वारा निम्नलिखित में से कौन सा उपकरण बनाया जा सकता है?

Which of the following are desirable characteristics of a good textbook? a. Content b. Presentation c. Editing d. Big in size

The Heuristic method of teaching was advocated by:

Which teaching method proceeds from concrete concepts to abstract concepts?